(For advanced practitioners who already hear the Sound) This is the most complete description of how to work with the Nada during Meditation that I know (Link to Lecture).

The BEST reference I have found on the Nada Yoga. (From the First International Yoga Teachers Training Course at Munger, 1967-68)

Any practice or technique of meditation that brings about complete cessation of consciousness is called laya yoga. There are many sadhanas recommended in laya yoga and nada yoga is one. The word nada is derived from the Sanskrit root nad, meaning 'to flow'. Hence the etymological meaning of nada should be a process or a flow of consciousness. Ordinarily the word nada means sound. There are four stages of manifestation of sound according to frequency and subtlety or grossness. The four stages are: (i) para, (ii) pashyanti, (iii) madhyama and (iv) vaikhari. These four stages of sound should be understood scientifically. Para nada

Para means 'transcendental, 'beyond' or 'the other side'. It is beyond the reach of the indriyas, or sense organs, and the mind and other means of cognition. Hence para nada is the transcendental sound. It is indicative of a truth that there is a sphere of super-consciousness where the sound is heard in different dimensions.

Students of classical music are aware of the fact that every note is made up of different numbers of vibrations per second. They vary in length, speed and pitch. In Indian music these vibrations are called andolana. In one second a sound may make many thousands of vibrations. Above a certain level of high frequency, sound becomes inaudible and can only be perceived subjectively. The ears cannot receive such sounds that are vibrating at a very high rate. Therefore, we are not aware of all the sounds that are present in the cosmos. Sounds having a very high frequency are transformed into silence. Beyond a certain limit, the ears do not have the capacity. No one can hear or understand a sound like that even if it is present.

Para or transcendental sound has the highest vibration frequency. This intense vibration faculty makes para inaudible. Various texts mention that para sound has no vibration. It is a sound that has no movement and therefore no frequency. It is a still sound, but we cannot conceive of a sound that has no vibration, no movements, no motion. When a sound goes to its maximum pitch, it attains a sudden stillness, and that is para nada.

In the Upanishads, the sound of Om is said to be the manifestation of para. The audible chant of Om which we produce is not para because it is physical, subject to our hearing, understanding and logic. Therefore, the audible Om cannot be called the transcendental Om. Para is a cosmic and transcendental sound devoid of all movement. It is both still and infinite. It has shape and light too. Its nature is jyoti (light). It is different from all sounds usually heard or conceived. The Upanishads clearly state, "That is Om, that sound is Om." Pashyanti

The second stage of sound, which has less frequency and is more gross than para, is pashyanti. It is a sound which cannot be heard, but it can be seen. Pashyanti in Sanskrit means 'that which can be seen or visualized'. The ancient scriptures maintain that sound can also be perceived. How does one see a sound? Well, have you ever heard a piece of music in a dream? This particular dimension of sound, as it is in dream, is called pashyanti. It may be called a mental sound, which is neither a conscious sound nor a semi conscious sound. It is a subconscious sound pertaining to a quality of mind and not belonging to the quality of the sense organs, like the tongue or ears.

When I say out loud "Rama, Rama, Rama, Rama," it will be called vaikhari, but when I close my eyes and mouth and go in and repeat mentally the sound of Rama, visualizing its colour and form with the inner eye, it is known as pashyanti. When the word or the sound is heard in a sphere where one is not aware of the outer surroundings, it is called pashyanti. When every outer sound is extinct and you hear a new sound altogether unlike the nature of audible sounds, know it as a special sound or the nada of pashyanti. Madhyama

A form of sound having lower frequencies than para and pashyanti, but still subtler than the audible vaikhari form of sound, is known as madhyama. It is a sound produced in whispering. No audible effect is produced in it. Madhyama produces very minute vibrations in the act of a whisper. In an ordinary sound, two objects strike against each other in order to produce sound. But in madhyama no two things strike violently so as to produce audible sound. For example, when a sound is produced like 'thuck, thuck, thuck', it is called a gross sound. The word madhyama means 'in between' or ' middle', so madhyama means a middle sound, a whispering sound or the sound of a whisper. Vaikhari

The fourth and gross stage of nada is called vaikhari. Vaikhari sound is audible and producible. The spoken sound is vaikhari. It is produced by friction or by striking two things against each other. Its frequencies of vibration are conducted within a certain limited range.

To sum up, vaikhari is the gross quality of the vocal organs, madhyama is the subtler quality of the same physical organs, pashyanti is the quality of the subconscious or unconscious, and para is the quality of the soul. The universe and nada

According to nada yogis and the scriptures dealing with the subject of nada yoga, the nada brahma, or the ultimate and transcendental sound, is the seed from which the entire creation has evolved. A nada yogi believes that the world is but a projection of sound alone. The whole macro cosmic universe is a projection of sound vibrations. From that sound the whole world has evolved. In the Bible there is the reference: "In the beginning was the word, and the word was with God." This word is called the nada or the shabda. Sufis in India call it surat. Surat or shabda yoga is another name for nada yoga practice. The Sufi saints of philosophical temperament also believe that out of sound and form the world evolved. The nada yogis believe that the five elements, five karmendriyas, five jnanendriyas, the fourfold mind and the three gunas have evolved out of one eternal sound. It means that prakriti, the material, mental, psychic and intellectual universe, is all an outcome of nada brahma. This is the ultimate belief of all nada yogis. So a nada yogi believes in a reality which has manifested itself in the form of vibration. It is a vibration that either does not vibrate at all or at such a high frequency that it is beyond the reach of the human faculty.

The eternal or original nada has the highest rate of frequency and vibration. When any object vibrates at a tremendous and unimaginable speed, it becomes still. It means that the highest point of motion and vibration is stillness. And that nada appears to be the creative principle of all matter and the entire material substance.

Nada yogis contend that everything in the universe originated and evolved from the eternal and infinite nada. In this context a study of the Upanishads is recommended, with special reference to Nada Bindu Upanishad and Hamsopanishad.

Music is also a materialized form of nada and the movements of prana in the body are also nothing but the expressions of nada. The purpose of nada yoga sadhana is to find out the primal, the finest, the ultimate inner sound - the word or shabda. In order to discover this transcendental and non-empirical sound, the process starts from the external gross sound. From there the ultimate form of sound is conceivable only through going into the deeper realms of our consciousness. The centre of nada

There are different centres where the transcendental nada is said to be situated. Bhaktas try to find the centre of their ishta in anahata. Yogis try to find the centre of intuition in ajna. Vedantins try to find the centre of hiranyagarbha in sahasrara. Likewise, nada yogis locate the centre of nada in bindu. Bindu is the centre where the continuous, eternal, inaudible, unbroken and unbeaten sound goes on. For the purpose of the discovery of nada, it is true that the bindu has to be discovered primarily and finally.

Before venturing into the depth of this science, it would be better for the aspirant to locate or discover the mental, astral and psychic nature of the sound of nada. Different nada yoga practices are introduced in order to help the aspirant to get through the different psychic and non-physical sounds, before the consciousness can finally be attuned with the real nada. Practice of nada in bhakti yoga

The practices meant for bhakti yoga are also included as practices of nada yoga. When a bhakti yogi performs mantra japa, in the first stage he tries his best to maintain awareness of the sound produced by the mantra. After having developed a deeper awareness of the sound of the mantra, he stops producing an audible sound vibration and in the second stage tries to intensify his awareness on the basis of the mantra repeated in whispered tones.

When this task is accomplished satisfactorily, he stops whispering and repeats the same mantra mentally. He tries to hear the mental and subtle notes which, though inaudible, can be visualized through a deeper form of awareness. Sometimes at this stage, it is possible to actually experience hearing the same mantra internally. The bhakti yogi will feeling as if he has really chanted the mantra in an audible tone. When the awareness of mental mantra chanting is absorbing and the mind is completely fused in a deep realm of awareness, mantra or nada is transformed into a constant inaudible repetition which will appear to the aspirant on the plane of consciousness as audible; but it will be imperceptible and inaudible to others. This is the way to experience the nada in the practice of mantra yoga by bhakti yogis.

A few kriyas combined with bandhas and mantras should also be included in order to stimulate the dormant psychic regions. The aspirant should begin the task of discovering the first sound or nada by plugging the ears and listening to the inner sounds. When the practice is fairly advanced, the ears need not be plugged in order to commune with the different dimensions of sound. Instead one should try to commune with the inner sound during the stillness of the night without closing the ears. It is easy to apprehend the inner sounds at midnight or early in the morning. Diet of a nada yogi

The diet of a nada yogi should be light and easily digestible. Any food that sends quick influxes of blood to the brain is undesirable. Food which causes hypertension or high blood pressure should be avoided. The normal nutritional supply required to maintain normal functioning of the body should be provided. Music and nada yoga

Music is also nada yoga, where the music is rendered absolutely scientific and classical in order to experience the nada. The development of musical systems in the past was done strictly in accordance with the views of nada yoga sadhanas. The well-known and most ancient Sama Veda is always sung with a scientific exactness and in accordance with nada yoga sadhana.

At different stages of conscious awareness, the mind is easily attracted by different waves of nada. Certain vibrations of nada seem to be agreeable at a particular time, while others are disagreeable at a particular time of the day. Certain combinations of nada are agreeable to some people and disagreeable to others. In music these nada vibrations are known as raga or musical notes. A raga having short vibrations is not relished by some. The morning music of India, like the Bhairava or Bhairavi raga, is appealing to a few, but not to all. I like the midnight music of India, the Malkos, the Durga or the Jogia ragas. The evening raga, like Bhimpalasi, is also popularly appreciated. Generally, girls and boys of a tender age prefer Bhairavi. This shows that the mind reacts differently to different sound waves at different times.

Music can be taken up as a spiritual sadhana, as a preliminary practice, or just as a pleasant, interesting and inspiring sadhana of nada yoga, through which the mind can be attuned to the subtlest vibrations before proceeding to discover the last transcendental sound of nada. Time for practice

One can practise nada yoga whenever one is free. A beginner should practise between midnight and two a.m., the period free from the disturbing influences of external sound. Absence of light in the atmosphere also aids the practice. These help to introvert the mind. Precautions

Some precautions should be borne in mind because nada yogic sadhana can bring about a manifestation of any sound. Sometimes, if the practitioner has a weak state of mind, there may be a buzzing in the ears throughout the day. Sometimes he may hear the sound of a bell or various other sounds. Manifestation of these different sounds disturbs the peace of the aspirant. If the sound continues to agitate the mind, the nada yoga sadhana should be given up. It is sure and certain that by correct practice of nada yoga, inner sounds are developed by stages. They are not heard at any other time during the waking period.

The nada yogi is capable of hearing a voice in the waking state if he is at a very advanced stage. It appears as if someone is whispering into his ears. This is a kind of Siddhi; a power to hear a sound from an unknown. Preparation for nada sadhana

First of all, the nada yogi should practise moola bandha, vajroli/sahajoli mudra and yoga mudra. These are important. When these have been learnt, one should practise kumbhaka and focus the consciousness on bindu. Pranayama also forms an important preliminary and essential part of this sadhana. There are many pranayama practices that can cause nada to manifest. One is moorcha. Brahmari should also be practised, with the ears plugged, and the eyes pressed with the fingers as in shanmukhi mudra. The upper and lower teeth should be kept apart, the jaw unclenched. Then the actual practice of nada yoga should follow. Practice for the manifestation of nada

Sit down on a firm pillow in a squatting position, placing the soles of the feet on the ground with the elbows resting on the knees or thighs. For some a lower pillow will be comfortable and for others a higher one. The most important point here is that the coccyx and the perineum should be pressed against the pillow at the point of mooladhara, and therefore the pillow should be round and hard. Thus, without contraction of the anus, the mooladhara chakra should be pressed by sitting on a high and hard pillow.

After practising moorcha pranayama, shanmukhi mudra, moola bandha, vajroli/sahajoli mudra and brahmari pranayama first for a few minutes, start the practice of nada yoga in the following manner. Plug both the ears. Take the consciousness to bindu and try to find out or be aware of any sound that is internal. This internal sound may resemble anything. It may be like a cloud passing or a stream flowing, the sea roaring or a bell ringing. It may also be the sound of a flute, the rhythm of a guitar or the sound of birds chirping in the evening at the time of sunset. It might be in the form of an awareness of the distant ocean or the sound of a thunderbolt. Or it might even be the vision of a starry night devoid of any sound. These internal sounds are to be discovered by the aspirant.

If it is difficult to discover a sound in bindu, circulate your awareness in sahasrara or ajna, or in the centre of the brain, or in the right or left eardrums. Or focus your mind at chidakasha or at the centre of the third eye until you are sure to get the sound. The method of discovering the sound is simple. Instead of imagining a sound, make your mind one-pointed, then discover the first sound and pursue it up to the end. One inner sound of nada should be followed to the extent where it becomes more and more clear and prominent. As soon as it is clear and prominent, another sound (a different sound altogether) is heard and felt in the background.

When you discover the second sound, give up the first one and follow the second. For instance, close your ears and listen to the first sound, for example, the evening sound of birds. Keep on listening to it. When it becomes completely clear and distinct, find another sound manifesting behind, like the sound of a nightingale. Now continue to follow your consciousness up. Move on from the sound of the evening song of the birds. Let the music of the nightingale become clearer until the first sound has gone. When that is completely distinct and clear to your consciousness, another sound will be heard in the background. The forthcoming sound may be like the sound of crickets going 'chin, chin, chin, chin, chin'. When this sound also becomes very clear to you, reject the previous one, the singing of the nightingale, and pick up this new one. This will also become clearer after some time, and will be replaced by a fourth one. This process continues until the consciousness is completely lost, or the consciousness is completely devoid of the contents of the mind. Nada in the koshas

These sounds which are heard are true. They are the symbols of the content of the mind and of consciousness. The mind rests on these symbols and it goes in quickly with their help. These sounds are experiences of the deeper layers of consciousness belonging to annamaya kosha, pranamaya kosha and manomaya kosha. These sounds are not imaginary. They may be understood as the vibrations of different spheres of one's existence. The physical, pranic, mental, supra-mental and the ananda or atmic are the five spheres of one's existence. In different spheres of existence different sounds are heard. There are physical sounds first, but when consciousness becomes fine and transcends the physical plane, it will come in touch with the subtle sounds of the movements of pranic consciousness in the physical body.

The entire range of human consciousness is divided into three, or subdivided into five parts. The conscious state consists of the annamaya and the pranamaya koshas, and these two bodies are made up of food and of prana. The second sphere of the personality is comprised of manomaya and vigyanamaya koshas and mainly contains mental and astral matter. The third dimension of consciousness is the realm of anandamaya kosha, which is full of bliss.

In the practice of nada yoga, the manifestation of nada takes place in accordance with the relation established between the mind and the other spheres of consciousness. For instance, if the mind or consciousness is rooted in the physical body, by closing your ears you will hear the sounds or vibrations produced by the movements of the heart, lungs, brain, blood circulation and the process of metabolism and catabolism that are going on inside the body.

If consciousness has penetrated the pranamaya kosha, you will hear many more sounds. And if the mind has gone deeper into the anandamaya kosha, then all other sounds will disappear and in its place the effect of nada yoga will remain.

It is difficult to tell which particular nada belongs to a particular sphere. In India, illustrations are given in the form of symbolic stories. The individual consciousness, which keeps on soaring high and discovering the transcendental notes, is symbolized as Rishi Narada in Indian mythology. Without denying the historical existence of Rishi Narada, the esoteric significance of the word Narada should be understood. Narada is supposed to be a rishi who has a veena in his hands. In nada yoga, the sound of the veena is considered to be the music of a very high sphere. According to all the traditional nada yoga cults, the nada of the flute and veena belong to that sphere of consciousness where dwaita bhava, or the duality of consciousness, ceases to exist. Nada yoga in the Bhagavata

Nada yoga is illustrated in the great book entitled the Bhagavata (different to the Bhagavad Gita). A symbolic and allegorical description of nada is given in the form of the story of Krishna. It says, "Lord Krishna left his place at midnight and went into the jungle. It was the full moon night of the first month of winter. He began to play the flute. The echo of the flute spread in the calm and undisturbed atmosphere. Music rose from the jungle and was heard by the gopis (the village cowherd girls). When they heard the sound of the flute, they immediately left their houses and their husbands, forgetful of all that was taking place. They ran, without consideration, to the place from where the nada from the flute was emanating. They started dancing about the flute player. After some time, it so happened that each one found herself dancing individually with Krishna."

The story seems fantastic, but in fact it is not properly understood by people of the world. It is understood only by nada yogis. They consider Krishna to represent that higher sphere of consciousness where the nada of that sphere emanates during the deepest state of nada sadhana. When the emanation of flute music takes place, the senses, the indriyas, or the sense-consciousness, forsake their respective objects and withdraw from their respective centres of pleasure and perception. They recede and go back to the place from where the flute sound or the nada is emanating. There the senses dance around the nada. In that state, the senses completely withdraw from the outer objects. In other words, a yogi may say that dharana has taken place and dhyana is about to dawn.

In Sanskrit the word krishna means, 'that which draws' or 'that which attracts'. It is derived from the root word karshan. So the word krishna means 'the puller', 'the with drawer', or 'the attractor'. It also means 'farmer', and, the word gopi means 'cow'. In Sanskrit, go means 'senses', 'cow', 'poor', 'humble' and the 'whole perceptible universe'. Ordinarily, the word gopi means 'the daughter of a cowherd family'. Symbolically, gopi means 'senses'. And who are the husbands of the senses (the gopis)? It may be said that for the eyes, the form is the husband and for the ears, sound. When the music of a flute is heard, the sense of hearing leaves or withdraws itself from the outer audible sounds and merges itself in the inner nada. This process is called pratyahara. Nada yoga and Kabir

A famous nada yogi named Kabir says in one of his poems: "Who is there playing upon a flute in the middle of the sky? On the confluence of the Ganga and Jamuna, the flute is being played, and the confluence of three rivers - Ganga, Jamuna and Saraswati - takes place in trikuti. Oh, this is a meeting point of Ganga and Jamuna. The sound emanates from the north! Cowherd girl, hear the sound of the flute and lo, they are all hypnotized by the nada."

The ultimate experience in nada yoga is a sound higher than the sound of the flute. The music of the highest sphere is not of the flute, veena, thunderbolt, clapping or any musical instrument. It is not even similar to the classical music of either east or west. The music of the highest sphere is 'anahad nada'. Anahad nada and anahata nada

What is anahad nada? No one has been able to tell even till this day. Some say that is the cosmic sound of Om. Others say it is like brahmari, a sound resembling the unceasing and unbroken sound of the honeybee. Some say that it is the beat of the heart.

Some people call it anahad, while others call it anahat. These two words convey two different meanings. Anahatderives from 'an' + 'aahat'. 'An' means 'no', 'aahat' means 'that which is striking, hammering or beating'. Therefore, anahat means 'no beating or striking of two things'. Usually a sound is produced by two things striking against each other, but anahat is a sound which is not produced by striking. It is spontaneous and automatic. Some scholars say that the nada is anahad. 'An' means 'no' and 'hada' means 'boundary' or 'compound'. Hence, anahad means 'without any limit, without any boundary,' or 'without any specification'. It is a sound upon which no limits can be put. It can be any sound. Nada yoga and Gorakhnath

The great guru Gorakhnath, disciple of yogi Matsyendranath, gives a description of nada yoga. He writes, "Oh sadhu! Do japa of Soham. That japa should not be done through the mind. It should be done through the consciousness, so that even when you are engaged in your day-to-day activities, you should be aware of 21,6000 rhythms of your breath throughout the 24 hours of the day, at the rate of 15 or 19 rounds per minute (which means 900 and more breaths per hour). Anahad nada will emerge and will manifest on its own." He says further, "There will be light in the spinal cord. The solar system of the surya nadi will be awakened. You will feel an indescribable vibrating sound from every pore of your body and that will be like Om or Soham." The ultimate nada

The ultimate nada that manifests in the highest sphere of consciousness is indescribable. It is a sound coming from the sphere beyond the anandamaya kosha. A nada yogi believes that the actual point where the individual consciousness fuses with the cosmic consciousness is in the highest state of nada. The aspirant or sadhaka realizes his higher consciousness in nada and sees the whole universe in the form of sound.

(Source: https://www.reddit.com/r/Meditation/comments/3hqxvv/the_nada_sound_a_synthesis/)

Update: After finishing this post, I couldn't stop from researching. So I am posting a collection of research materials.

I have been interested in the internal sound and how to integrate it in my meditation sessions. Ever since I was a child, I could hear it loudly, sometimes as loud as people speaking right in front of me. So I took it on myself to collect all the information I could, from Vedantic and Buddhist sources and even personal stories and forum discussions. Here it is, a synthesis of all I collected. Beware that the information is not very well integrated, being just a mix of everything I could get my hands on. I put this article here because it is visible and people could comment on it.

Definition

In the West it is called tinnitus and defined as "a medical condition in which you hear a continuous noise in your ears", however, in the Eastern traditions it has been considered a great way to deepen meditation.

Some call it "one's own sound" or "the sound of one's own nature" because it is not caused by any external objects. Other call it the stream (nada means stream in sanskrit) because it kind of sounds like the roaring of a stream, or even "the sound current". Because it can be heard when there is silence around, it is also said to be "the sound of silence". Being continuous, it is named "the eternal sound" and being located inside the mind, it is also named "infinite space". Buddhists call it "Divine Ear". Mystical texts attribute it to the Logos, or AUM, the original sound of creation.

Characteristics

A main characteristic of Nada is that it is not created at will, so, it just is, but in such a way that it is there only when attended to, and disappears beneath the other sounds when not minded.

Another characteristic is that it is always present and self evident, intermixing into all the other sounds, even when not meditating. Like the concept of self which binds to all our experiences and infuses itself into all mental states, this sound is also permeating the mental chatter and external sounds.

The Nada sound is not an actual sensorial perception, it doesn't lend itself to being described very well by similarity with the external sounds, being somewhat "featureless" and "formless". It does not appear to be coming from a point in space, but appears directly inside the head, and as such it is compared to an "unlimited space".

Descriptions

There have been many attempts to describe what it sounds like by comparing it to objective external sounds. I compiled a list of its descriptions but it is by no means complete. Here I go, it's a mouthful:

It is like the ocean, like bells ringing, a flute, a bee swarm, crickets or grasshoppers, like a vibrating crystal, a musical instrument, a flute, like birds chirping at sundown, an unearthly sparkling sound, a sonic pressure - the noise made by gas escaping with pressure from a pipe, a symphony of scintillating vibrations, the distant murmur of the sea, a bell which rings or chimes, like the sound of small pieces of glass rustling together, and has a silvery and sparkling quality to it.

Practices associated with Nada

Here's the interesting (practical) part:

The basic practice is to listen to the sound in a state of open awareness. It is at the same time a form of concentration and witnessing.

Some recommend identification with the sound, in all its nuances. Other texts suggest to focus on the most subtle part of the sound.

Other texts tell us to listen to it in a non-interfering manner, just be with it, nothing to do, rest the mind in it. To see the body and mind as existing here and now, in the space of consciousness, permeated by the sound of Nada.

Others instruct to follow its changes, left or right, forehead or back of the head, the changing of its character, e.g: sometimes like a river, other times like crickets.

There is an advice to listen to it with extreme vigilance, like a samurai who is about to duel in a sword fight, when even a second of inattention could cause him to lose his life. Another metaphor - imagine a deer that becomes absorbed and motionless on hearing the sound of people approaching - that kind of acute yet non-selective attention.

There are some who emphasize the meaning we place on it, the intention with which we listen to it, the value we give it, and having an attitude of gratefulness while we surrender to it.

There is also a technique to be mindful of its sub-sounds. The Nada is formed of a few superimposed sounds - for example, a roaring river and also at the same time chirping and a very high pitched flute. Fix on the loudest one, then identify the secondary sub-sounds, pick one of them, focus on it until it also becomes loud and clear, then repeat the process with the other sub-sounds. These sub-sounds could be variations of the initial sound: louder, higher pitched, or having a different character, or coming from a different direction.

There are some who suggest to find the most subtle part of it and ignore the rest, metaphorically the same way we should focus our inner awareness while ignoring all the distractions in meditation.

Effects

The Nada sound meditation has a calming effect on the mind and induces a state of peace. It gives a sense of stability, being uninterrupted and always there. By letting it fuse with you and permeate your body and mind, it helps develop a more elevated and subtle perception of oneself.

Intense listening to Nada leads to a state of profound awareness of the heart. It acts like an anchor, reminding us of our true nature, helping us remain focused on the present moment. Like breath, it is always at hand in meditation. It helps develop concentration and stops ordinary thinking because you cannot be aware of it and at the same time lost in thoughts.

Being a powerful sensation, it helps turn the senses inwards - pratyahara. It induces a state of transparency and void. It reduces the ego and the feeling of ordinary I-ness. It induces a rarefied, purified perception of one's body, as if it became weightless and immaterial. Even Buddha is said to have reached enlightenment by meditating to the Nada sound.

That's about all I got, but please expand with your own sources and personal experiences.

TL;DR: Silence is creative.

The Nada is often described as the Sound of Locusts on a summer's evening.

A short film on Naam: The Unstruck Sound can be heard at 6:57 - 7:00 and again at 23:30 - 23:40

The Shining: The Unstruck Sound is heard each time Danny "shines"

Supernatural things occur in a very natural way. There is tremendous overlap in descriptions of Tinnitus and the Anahata Nada. This Post gives several examples of sounds like the Sehaj Dhun, and This Video gives several examples of Tinnitus. Consider Silence, the Nada and Tinnitus; I see them as different perceptions of the same Experience. For most, the intensity of the Sound is low and the Mind blocks it out as background noise to create a baseline known as Silence. For some, a variety of medical conditions increase the intensity of the Sound such that it is incessant, irritating and cannot be blocked by the Mind. Tinnitus is the blanket term used for this. A small handful, through the practice of Discipline develop the skill to hear what their Mind chooses to ignore. This State of Awareness is a great Blessing. A person should strive to maintain it at all times.

From Ashtanga Yoga: Practice and Philosophy by Gregor Maehle (Page 211):

[I.36] Steadiness of mind is also gained from perceiving a radiant light beyond sorrow.

The light talked about here is the light in the heart lotus. Meditating on the light in the heart or the heart sound is one of the main meditation techniques in yoga. The Yoga Taravali and the Hatha Yoga Pradipika have as their main theme hearing the unstruck sound, the heart sound (anahata nada).

In this sutra the light in the heart is mentioned, and the heart is the origin of the mind. As the Upanishads state, mind and intellect are projected out of the heart and will be reabsorbed into it eventually. Sutra III.34 says that contemplating on the heart will lead to the understanding of the mind, while sutra III.33 declares that everything will be known through the rising light of pure intellect. The light of pure intelligence or intellect is situated in the heart lotus. By meditating on this light, steadiness of mind is achieved.

The light is said to be “beyond sorrow” because sorrow arises from the various forms of ignorance (avidya). When one sees the light in the heart, which is the effulgence of pure intelligence, this intelligence will dispel ignorance. Eventually it will produce discriminative knowledge, which is the end of suffering. In this sutra, however, only the light beyond suffering is seen, which is a more modest achievement. This means we get only a sneak preview of pure intelligence, enough to make the mind steady.

The other way of meditating on the light in the heart is to meditate on the notion of “I am” (asmita). This I-am-ness is produced from pure intelligence. If we reduce all of our thoughts to I am — or, in other words, if we retrace our thoughts to the notion of I am — this also makes the mind steady. All thoughts contain the notion of I am. In the thought process there are the thinker, the thinking, and the object thought about. For thinking to happen, the notion of I am must be there. If we remain aware of this notion, rather than forget ourselves or forget that it is we who think, then the mind becomes steady.

Link to PDF copy with countless jewels of wisdom for practice in the form of questions/answers and messages from the Master.

Excellent series of talks on the Vijnana Bhairava Tantra aphorisms about the Anahata Nada

[35] One should meditate on the inner space of the medial nadi (sushumna) situated in the central axis of the body (the spinal column), which is as slender as a fibre of the lotus stem, and then by the grace of Devi, the divine (form) is revealed.

[36] By using the hands (as tools) to block the entrances in all directions, the eyebrow centre is pierced and bindu (or light) is seen. Being gradually absorbed within that, the supreme state is realized.

[37] Whenever one meditates upon the subtle lire, in the form of a tilak (like the mark on the forehead), or on the bindu at the end of the shikha, a condition of agitation and shaking is produced, followed by absorption and dissolution in the cave of the heart.

[38] One, who is adept in listening to the unstruck sound in anahata, (which is) uninterrupted like a rushing river, attains the supreme state of Brahma by mastery of shabdabrahman, the form of Brahman as sound.

Teachings of Pir-O-Murshid Hazrat Inayat Khan as transcribed by his students from his lectures and talks given between 1914 and 1926

Volume II - The Mysticism of Music, Sound and Word Part I: The Mysticism of Sound Chapter VIII ABSTRACT SOUND

Abstract sound is called Saut-i Sarmad by the Sufis; all space is filled with it. The vibrations of this sound are too fine to be either audible or visible to the material ears or eyes, since it is even difficult for the eyes to see the form and color of he ethereal vibrations on the external plane. It was the Saut-i Sarmad, the sound of the abstract plane, which Muhammad heard in the cave of Ghar-i Hira when he became lost in his divine ideal. The Quran refers to this sound in the words, 'Be! and all became.' Moses heard this very sound on Mount Sinai, when in communion with God; and the same word was audible to Christ when absorbed in his Heavenly Father in the wilderness. Shiva heard the same Anahad Nada during his Samadhi in the cave of the Himalayas.

The flute of Krishna is symbolic of the same sound. This sound is the source of all revelation to the Masters, to whom it is revealed from within; it is because of this that they know and teach one and the same truth.

The Sufi knows of the past, present and future, and about all things in life, by being able to know the direction of sound. Every aspect of one's being in which sound manifests has a peculiar effect upon life, for the activity of vibrations has a special effect in every direction. The knower of the mystery of sound knows the mystery of the whole universe. Whoever has followed the strains of this sound has forgotten all earthly distinctions and differences, and has reached that goal of truth in which all the Blessed Ones of God unite. Space is within the body as well as around it; in other words the body is in the space and the space is in the body.

This being the case, the sound of the abstract is always going on within, around and about man. Man does not hear it as a rule, because his consciousness is entirely centered in his material existence. Man becomes so absorbed in his experiences in the external world through the medium of the physical body that space, with all its wonders of light and sound, appears to him blank.

This can be easily understood by studying the nature of color. There are many colors that are quite distinct by themselves, yet when mixed with others of still brighter hue they become altogether eclipsed; even bright colors embroidered with gold, silver, diamonds, or pearls serve merely as a background to the dazzling embroidery. So it is with the abstract sound compared with the sounds of the external world. The limited volume of earthly sounds is so concrete that it dims the effect of the sound of the abstract to the sense of hearing, although in comparison to it the sounds of the earth are like that of a whistle to a drum. When the abstract sound is audible all other sounds become indistinct to the mystic.

The sound of the abstract is called Anahad in the Vedas, meaning unlimited sound. The Sufis name it Sarmad, which suggests the idea of intoxication. The word intoxication is here used to signify upliftment, the freedom of the soul from its earthly bondage. Those who are able to hear the Saut-i Sarmad and meditate on it are relieved from all worries, anxieties, sorrows, fears and diseases; and the soul is freed from captivity in the senses and in the physical body. The soul of the listener becomes the all-pervading consciousness, and his spirit becomes the battery which keeps the whole universe in motion.

Some train themselves to hear the Saut-i Sarmad in the solitude on the sea shore, on the river bank, and in the hills and dales; others attain it while sitting in the caves of the mountains, or when wandering constantly through forests and deserts, keeping themselves in the wilderness apart from the haunts of men. Yogis and ascetics blow Sing (a horn) or Shankha (a shell), which awakens in them this inner tone. Dervishes play Nai or Algosa (a double flute) for the same purpose. The bells and gongs in the churches and temples are meant to suggest to the thinker the same sacred sound, and thus lead him towards the inner life.

This sound develops through ten different aspects because of its manifestation through ten different tubes of the body; it sounds like thunder, the roaring of the sea, the jingling of bells, running the water, the buzzing of bees, the twittering of sparrows, the Vina, the whistle, or the sound of Shankha until it finally becomes Hu, the most sacred of all sounds.

This sound Hu is the beginning and the end of all sounds, be they from man, bird, beast, or thing. A careful study will prove this fact, which can be realized by listening to the sound of the steam engine or of a mill, while the echo of bells or gongs gives a typical illustration of the sound Hu.

The Supreme Being has been called by various names in different languages, but the mystics have known him as Hu, the natural name, not man-made, the only name of the Nameless, which all nature constantly proclaims.

The sound Hu is most sacred; the mystics call Ism-i Azam, the name of the Most High, for it is the origin and end of every sound as well as the background of each word. The word Hu is the spirit of all sounds and of all words, and is hidden within them all, as the spirit in the body. It does not belong to any language, but no language can help belonging to it.

This alone is the true name of God, a name that no people and no religion can claim as their own. This word is not only uttered by human beings, but is repeated by animals and birds. All things and beings proclaim this name of the Lord, for every activity of life expresses distinctly or indistinctly this very sound. This is the word mentioned in the Bible as existing before the light came into being, 'In the beginning was the Word, and the Word was with God, and the Word was God.'

Truth, the knowledge of God, is called by a Sufi Haqq. If we divide the word Haqq into two parts, its assonant sounds become hu ek, Hu signifying God, or truth, and ek in Hindustani meaning one, and both together expressing on God and one truth. Haqiqat in Arabic means the essential truth, Hakim means master, and Hakim means knower, all of which words express the essential characteristics of life.

Al-Haqq is the sacred word that the Vairagis, the adepts of India, use as their sacred chant. In the word al-Haqq are expressed two words, al meaning he, and Haqq truth, both words together expressing God the source from which all comes.

The sound Hu becomes limited in the word Ham, for the letter m closes the lips. This word in Hindustani expresses limitation because Ham means I or we, both of which words signify ego. The word Hamsa is the sacred word of the Yogis which illumines the ego with the light of reality. The word Huma in the Persian language stands for a fabulous bird. There is a belief that if the Huma bird sits for a moment on the head of anybody it is a sign that he will become a king. Its true explanation is, that when a man's thoughts so evolve that they break all limitation, then he becomes as a king. It is the limitation of language that it can only describe the Most High as something like a king. It is said in the old traditions that Zoroaster was born of a Huma tree. This explains the words in the Bible, 'Except a man be born of water and the Spirit, he cannot enter the Kingdom of God.' In the word Huma, hu represents spirit, and the word mah in Arabic means water. In English the word 'human' explains two facts which are characteristic of humanity: Hu means God and man means mind, which word comes from the Sanskrit Mana, mind being the ordinary man. The two words united represent the idea of the God-conscious man; in other words Hu, God, is in all things and beings, but it is man by whom he is known. Human therefore may be said to mean God-conscious, God-realized, or God-man. The word Hamd means praise, Hamid, praiseworthy, and Muhammad, praiseful. The name of the Prophet of Islam was significant of his attitude to God.

Hur in Arabic means the beauties of the Heaven, its real meaning is he expression of heavenly beauty. Zuhur in Arabic means manifestation, especially that of God in nature. Ahura Mazda is the name of God known to the Zoroastrians. This first word Ahura suggests Hu, upon which the whole name is built.

All of these examples signify the origin of God in the word Hu; and the life of God in every thing and being.

Hayy in Arabic means everlasting, and Hayyat means life, both of which words signify the everlasting nature of God. The word Huwal suggests the idea of omnipresence, and Huvva is the origin of the name of Eve, which is symbolic of manifestation; as Adam is symbolic of life, they are named in Sanskrit Purusha and Prakriti.

Jehovah was originally Yahuva, Ya suggesting the word oh and Hu standing for God, while the A represents manifestation. Hu is the origin of sound, but when the sound first takes shape on the external plane, it becomes A, therefore alif or alpha is considered to be the first expression of Hu, the original word. The Sanskrit alphabet as well as that of most other languages begins with the letter A, as does the name of God in several tongues. The word A therefore expresses in English one, or first; and the sign of alif expresses the meaning one, as well as first. The letter A is pronounced without the help of the teeth or tongue, and in Sanskrit A always means without. The A is raised to the surface when the tongue rises and touches the roof of the mouth when pronouncing the letter l (lam), and the sound ends in m (mim). The pronunciation of which closes the lips. These three essential letters of the alphabet are brought together as the mystery in the Quran. With A deepened by ain the word Ilm is formed which means knowledge. Alim comes from the same, and means knower. 'Alam means state or condition, the existence which is known. When alif the first and lam the central letters are brought together they make the word al which means 'the' in Arabic. In English all suggest the meaning of the entire or absolute nature of existence.

The word Allah, which in Arabic means God, if divided into three parts may be interpreted as 'the One who comes from nothing'. El or Ellah has the same meaning as Allah. The words found in the Bible, Eloi, Elohim and Hallelujah, are related to the word Allahu.

The words om, omen, amen and amin, which are spoken in all houses of prayer, are of the same origin; A in the commencement of the word expresses the beginning, and M in the midst signifies end; N the final letter is the re-echo of M, for M naturally ends in a nasal sound, the producing of which sound signifies life.

In the word Ahad which means God, the only Being, two meanings are involved by assonance. A in Sanskrit means without, and Hudd in Arabic means limitation.

It is from the same source that the words Wahdat, Wahdaniat, Hadi, Hada and Hidayat all come. Wahdat means the consciousness of self-alone; Wahdaniat is the knowledge of self; Hadi, the guide; Hada, to guide; Hidayat means guidance.

The mystery of Hu is revealed to the Sufi who journeys through the path of initiation. The more a Sufi listens to Saut-i Sarmad, the sound of the abstract, the more his consciousness becomes free from all the limitations of life. The soul floats above the physical and mental plane without any special effort on man's part, which shows its calm and peaceful state; a dreamy look comes into his eyes and his countenance becomes radiant, he experiences the unearthly joy and rapture of Wajd, or ecstasy. When ecstasy overwhelms him he is neither conscious of the physical existence nor of the mental. This is the heavenly wine, to which all Sufi poets refer, which is totally unlike the momentary intoxication's of this mortal plane.

A heavenly bliss then springs in the heart of a Sufi, his mind is purified from sin, his body from all impurities, and a pathway is opened for him towards the world unseen; he begins to receive inspirations, intuitions, impressions, and revelations without the least effort on his part. He is no longer dependent upon a book or a teacher, for divine wisdom, the light of his soul, the Holy Spirit, begins to shine upon him.

As Sharif says, 'I by the light of soul realize that the beauty of the heavens and the grandeur of the earth are the echo of Thy magic flute'.

Reference: https://wahiduddin.net/mv2/II/II_8.htm

Edward Salim Michael has identified himself as primarily Buddhist, by that I mean a disciple of the Buddha, therefore I classified his work under the Buddhist tradition, despite it having some yogic terms like 'nada'.

The reason why I included him in this was because he was a very prominent influencer in Ajahn Amaro and Sumedho's teaching on the 'sound of silence'. As you read below, you can find that his teachings are very similar to those described by the Buddha.

His book "The Law of Attention"

Chapter 10

The value of this form of meditation cannot be overstated, especially for those who do not yet know where their attention should be directed, and who thus experience great difficulty retaining their concentration during meditation.

Having taken his meditation posture, and prepared himself mentally and physically—by quieting his mind, relaxing, and feeling a deep global sensation of his body—the seeker should now decide firmly not to move any more.

Closing his eyes, he should remain as still as possible, listening internally with sustained attention. If he can be inwardly quiet enough and deeply absorbed in the search, he will, if he is truly persistent, suddenly become aware of an unusual, feeble sound that can be heard deep inside the ears and head, concealed from him before and obscured by the din of his incessant mental restlessness.

Chapter 11

When the aspirant has recognized this Nada and familiarized himself well enough with it, he will perceive that, contrary to the ever-changing inner and outer conditions that he was used to up to that moment, this mystical sound has a strange unearthly continuity about it.

It can be compared to the soft whisper of the wind and the continuous hissing noise of the ocean waves, with a shrill “ultra” sound on top of it, composed of all the harmonics in the universe. On higher spheres, this sacred Nada will have a strange sort of silvery aspect to it, somewhat similar to the uninterrupted jingling sound of very little pieces of glass, with other smaller, ever more subtle sounds superimposed on it, until finally these finer sounds seem to disappear into infinity.

Chapter 3

When he takes the Nada—this mysterious sound which resembles the constant lapping of the ocean waves or the gentle murmur of the wind added to by a strange silvery timbre containing ever more delicate, crystalline harmonics—as the main support for his meditation, the seeker must remain constantly attentive and follow the continuity the sound has.

However, he should not forget that he is only using it with a view to succeeding one day in finding himself connected to another state of being in himself, beyond time and space, and not just simply to hear it.

Indeed, this sound is not a goal in itself; it merely comprises a temporary method intended to assist the aspirant’s concentration while he is trying to meditate.

Chapter 12

In the beginning of their quest, it is necessary for most people to make very great and sustained efforts with the utmost sincerity and determination. But they also need some definite thing to hold onto that can assist and guide them in this difficult spiritual journey and prevent them wandering blindly, trying to find the secret door to their True Being, hoping by chance to fall upon it.

That is why this inner mystical sound is like a precious sacred rope thrown down by Divine Grace to a drowning seeker—by the aid of which he may eventually pull himself out of the dark pit of his lower nature up to the light and vast expanse of his higher consciousness.

Chapter 14

When the aspirant succeeds in holding onto this sacred sound in such difficult conditions without losing it, a moment will finally arrive when he will become strangely distant from himself, and he will start viewing everything around him from another perspective altogether. He will feel that his vision seems to have inexplicably receded to the outside top part of the back of his head, from where he silently and impartially begins to witness all that is taking place around him. Everything will then be seen to be in a constant state of flux. From this uninvolved position, he will perceive that there is absolutely nothing permanent in any animate or inanimate object that meets his gaze.

The whole panorama of outer existence will appear to unfurl in front of him as a sort of strange and fantastic dream. And behind it all, he will mysteriously see through his mind’s eye, so to speak, the unity of all things—”That” which is pervading him and everything else at the same time.

Chapter 28

If the aspirant can attain the stage where his attention is held without fluctuating, then he will begin to feel a most subtle “interiorization” and “descent” into himself gently taking place. A curious heat will start spreading from his abdomen across his body, and a most unusual feeling of continuity of being will pervade him. The singular feeling of being mysteriously weightless will arise in him as if suspended in space like a seemingly immobile cloud hanging in the sky on a windless day, gradually changing to that of beginning to merge into and become the space itself. A most fine and ethereal energy will delicately permeate his whole being, miraculously transforming his feeling of himself and his consciousness. This extraordinary sensation of transparency of being and of consciousness will bring with it an unparalleled felicity and delicious peace beyond any words.

Furthermore, this wondrous Nada will sing its mysterious song inside his head, and his head will seem to become strangely translucent, with his consciousness extending out in all directions around him.

This sublime Nada will sing in his ears with such supernal beauty and intensity that the entire Cosmos will appear to be vibrating with it. Nothing else will seem to exist but this enigmatic song of the Divine, composed of all the subtle harmonies and ultrasounds in the mystical world, ever vibrating through space far into infinity—this strange song eternally giving out a secret message for those who have ears to hear and the sensitive intuition to understand and appreciate it. It could even sometimes seem to the aspirant that this primordial sound or vibration is the Divine!

Fruits of Awakening Chapter 1

Over the course of numerous attempts to remain attentive and present to himself during his meditation sessions, the aspirant will notice, with consternation, that after barely a few minutes (or even a few seconds), he is swept away by intrusive thoughts or images which constantly throng in his mind, and once again he finds himself enshrouded in this inexplicable and troubling absence to himself in which he sleeps, so to speak, in many cases for a long time, before realizing what has happened to him! Only when he is called back to himself by suddenly regaining consciousness does he realize that he had been plunged once again into that foggy state of daydreaming and strange inner absence; and, observing the difficulty he experiences when avoiding sinking down into it, he will begin to understand the true meaning of “Awakening” spoken about by the Buddha !

In the Silence of the Unfathomable

If, during his meditation sessions, the aspirant succeeds in his concentration becoming truly sustained and unfluctuating for a sufficiently long period, he will then feel overcome by a strange and subtle joy which will flood his being and dazzle him; a joy which is not of this world accompanied by a tranquil bliss, which will help and assist him in all his future efforts to remain concentrated, whatever the spiritual practice to which he is devoting himself.

His Book "Songs of Naropa"

Whether we are alive in a physical body or have passed on and are in the bardo state, the most important thing is to be stable-minded and level headed. Be steady in yourselves, and do not become totally overwhelmed by experiences; do not immediately get carried away by whatever takes place. This is an important quality to cultivate. Other- wise, whenever we feel pain or anxiety, we will be totally caught up in it. Train now to be more balanced in your response to your emotions. Cultivating this quality through Dharma practice makes an incredible amount of difference as to whether we take an unfortunate rebirth or a good one. During the bardo state, it is said that we encounter the natural sound of dharmata, the intrinsic and empty lights, colors, and sounds. We can grow accustomed to these right now. Train first by sitting with closed eyes. At first everything is dark and we don't see a thing, but eventually shapes start to appear. There are bits of light that takes different forms, perhaps moving; maybe green, yellow, blue or red. After a while it is possible that these formations of light will start to become bigger. They could even become quite overwhelming, but you should remain completely relaxed. These appearances are not made out of anything. They are insubstantial, and there is no real place that these formations come out of, or dwell. There is nothing to be astonished about; they are merely an expression of the empty nature. Once we grow slightly accustomed to these light formations that are the naturally empty lights of the innate nature, we have developed a kind of steadiness that will help us not to be overcome by the natural lights of dharmata in the bardo.

Similarly, we can grow accustomed to the intrinsic sound of dharmata that occurs in the bardo state by sitting down in a quiet place with no noise and paying attention. We should direct our concentration towards our hearing, not in an extroverted way, but tuning into a subtle sound that is present all by itself. Sometimes it helps to clench your teeth slightly and listen. There is a subtle roaring which you can hear more and more if you focus. It is not the sound of physical things clashing together, like a drum or any outer material objects. It is the sound of our own nature. When we pay attention, we find that the sound is not coming from anywhere, it remains nowhere, and it is not made out of anything at all. While looking into the identity of this intrinsic sound, there is no identity to find. It's totally insubstantial. Simultaneously, there is the hearing of this sound vividly and distinctly. This is identical in nature with the natural sound of dharmata during the bardo state. If we can relax into the hearing without being apprehensive or caught up in it, we can avoid being overwhelmed by the natural sound of dharmata in the bardo state.

Haṭharatnāvalī is a one of the important classical hatha yoga text this text was composed in the late 17th century by the Yogi Śrīnivāsa Bhatt.

Atha Nādānusandhāna: - in Meditative prospective A great yogi, who experiences a state of samādhi by meditating on the nada, experiences an inexplicable joy in his heart. Through constant practice, indifferent and with restraint, a yogi must resort to Nāda alone, who in a very short time attains the state of unmanī.

Method of Nādānusandhāna practices

A seeker should listen to the inner sound of the body by closing both his ears with cotton wool. Until his mind attains stability, one should concentrate on that inner sound i.e. Nāda. Various sounds are heard in the initial stage, as the practice goes on, even subtler sounds are heard [5]. In the beginning of the practice, sounds like the sea, thunder, big drums and waterfalls are heard. In the middle stage, sounds like small drums, conch shells and bells are heard. While at the end sounds like small bells, harp and the hum of bees are heard. Thus, different sounds are heard within the body. A sādhak becomes like a bee by constant practice of nādānusandhāna, like a bee that tastes nectar, not caring for the aroma. Similarly, the seeker does not run after the distractive thoughts by getting absorbed in the unstruck sound. Leaving all thoughts and subjects, always following the nāda, one merges into the nāda.

Different states of Yogāvastha

In the practice of Nādānusandhāna Arambha, ghata, paricaya and nispatti are the states of yoga described in all traditions of yoga. When a yogi attains the ārambha state, he develops a brilliant physique, deep insight, perfect well-being, sweet fragrance and contentment in the heart while enjoying emptiness. He has penetrated the brahmarandhra, nada emanates from sūrya and he hears a divine, unstruck, resounding sound. In the second state of ghata, the vāyu (prāna) passes through the middle path (suşumna), stability in asana is gained and the yogi becomes like a cupid. Moreover, the vişnu-granthi is pierced through, various sounds like that of kettle drum etc. are heard in the void (atiśünya), bringing in Absolute Bliss.

In the third state, one hears the sound of the kettledrum, (prāna) reaches the mahāśunya (centre of the eyebrows), which leads to the attainment of all siddhis (supernatural powers). The yogi attains spiritual happiness springing from Absolute Bliss and becomes free from all disturbances, sufferings, old age, premature death, hunger and thirst. When the anila (prāna) flows to the sarvapitha after piercing the rudragranthi, one attains the state of nispatti in which one hears the sounds of the finely tuned vīņā

Reference: https://www.allresearchjournal.com/archives/2023/vol9issue9/PartC/9-9-13-336.pdf

This has very interesting parallels.

Sikh Quotes on Celestial Sound

Such is the power of illusion or maya making souls deaf to the true teachings of the Sant Satgurus, that some think that the “Sound Current” mentioned by the Ten Sikh Gurus is only listening to the sound of outer music or hymns being sung. Living Masters have always initiated their disciples into meditation practice, and this includes the practice of hearing the Anhad Shabd (Unstruck Celestial Melody) within one’s self during meditation practice.

1. The Unstruck Melody that one seeks to hear, hear it thou in the instruction of the Guru’s. (Sri Rag M. 1)

2. (Within me) rings the Unstruck Melody of the Lord’s flute, yea, He in whose presence one’s mind is attuned to the sound (of the inner music). (Sri Rag, Kabir)

3. Seated in my higher mind, I live in communion with God and within me rings ever the Unstruck Music (of Bliss). (Sri Rag Var, Shloka M. 3)

4. He, the Lord, is immersed in the Unstruck Melody of the Word. (Asa, M. 1)

5. He, our God, is the King of the whole Universe. And there (in His Presence) rings the Unstruck Melody (of Bliss). (Sorath M. 5, Chaupadas)

6. The Lord’s Name has no form, no sigh, and it becomes manifest through the Immaculate God as the Unstruck Melody. (Asa M. 1)

7. In the cave of equipoise do I now have my seat. And the luminous Self of God has burst into me as the Unstruck Melody. (Asa M. 5)

8. At the (tenth) door rings the Unstruck Melody. The Lord echoes thus in every heart. (Vadhans M. 5)

9. The skinless drums produce the Music (of Bliss). The clouds rumble without the rainy season. And lo, without the clouds, it rains, if one reflects on the quintessence. (Sorath, Namdev)

10. Now I’ve closed all the nine Doors, and (at the Tenth) now rings the Unstruck Melody. (Sorath, Kabir)

11. All wisdom, all meditation is in hearing the gospel of the Perfect God and lo, immense is the joy of the Devotees of God, the Destroyer of worldly bonds, for within them rings the Unstruck Music of Bliss. (Suhi, M. 5)

12. Meditating on the Guru’s Word, the wholesome Unstruck Strains one hears. (Sri Rag M. 1)

13. Says Nanak: “Within him Perfect is whose Guru rings the Unbeaten Sound.” (Asa, M. 5)

14. How is one to perform Thy worship, O Thou Destroyer of coming-and-going? The Unstruck Melody (within) drums ever Thy glory. (Dhanasri M. 1, Arati)

15. What, pray, is the sign of the abode of gods? Therein rings the Unstruck Melody of the divine Word. (Ramkali Beni)

Ajahn Sumedho:

“As you calm down, you can experience the Sound of Silence in the mind. You hear it as a kind of high frequency Sound, a ringing Sound that’s always there. It is just normally never noticed. Now when you begin to hear that Sound of Silence, it’s a sign of emptiness — of silence of the mind. It’s something you can always turn to. As you concentrate on it and turn to it, it can make you quite peaceful and blissful. Meditating on that, you have a way of letting the conditions of the mind cease without suppressing them with another condition. Otherwise you just end up putting one condition over another.”

Also by Ajahn Amaro:

“Listening to the inner Sound brings the heart into a position of acute inner awareness. It is not that the inner Sound has some magical property. Rather, it is that bringing of the alert mind, bringing openness and receptivity to Sound, is symbolic of the presence of Ultimate Truth. The Sound is always there. We don’t have to create it. It is featureless. It is ever present. So it is a good symbol for Ultimate Reality itself.” “In the sutra the Buddha praised this method, the meditation on listening, as the best method for enlightenment. Ajahn Sumedho had been teaching the meditation on the Nada Sound for some years so he was tickled by this connection to another Buddhist tradition. He hadn’t realized that there had been so much emphasis on this in traditional Buddhist meditation practices.”

Reverend Guo Chin on Ajahn Amaro:

“When he [Ajahn Sumedho] first taught this method to the Sangha at Chithurst that winter, he referred to it as ‘the sound of silence’ and the name stuck. Later, as he began to teach the method on retreats for the lay community, he began to hear about its use from people experienced in Hindu and Sikh meditation practices. In these traditions, he found out, this concentration on the inner sound was known as nada yoga, or ‘the yoga of inner light and sound.’ It also turned out that books had been written on the subject, commentaries in English as well as ancient scriptural treatises, notably, “The Law of Attention: Nada Yoga and the Way of Inner Vigilance”, by Edward Salim Michael. In 1991, when Ajahn Sumedho taught the sound of silence as a method on a retreat at a Chinese monastery in the United States, one of the participants was moved to comment, ‘I think you have stumbled on the Shurangama Samadhi. There is a meditation on hearing that is described in that sutra, and the practice you have been teaching us seems to match it perfectly.’

From the Yoga Sutras of Patanjali:

[1:51] tasyāpi nirodhe sarva-nirodhān nirbījaḥ samādhiḥ

When the turnings of thought cease completely, even wisdom ceases, and contemplation bears no seeds.

Contemplation without seeds (Nirbija Samadhi) is a hyperconscious condition in which thought is calm and totally integrated. It leaves no seeds to mature into future thoughts, Wisdom realized without intellectual activity.

Nadanusandhana (Listening the the Anahata Nada) is a Manolaya practice (Dissolution of the Mind; a state where the mind gets absorbed into the object of meditation). It is Nirbija Samadhih. In this hyperconscious condition Wisdom is realized without intellectual activity, leaving NO traces to develop into Samskara (Impressions). This is the Power of listening to the Anahata Nada.

Clairaudience

"With his mind thus concentrated, purified, and bright, unblemished, free from defects, pliant, malleable, steady, and attained to imperturbability, he directs and inclines it to the divine ear-element. He hears — by means of the divine ear-element, purified and surpassing the human — both kinds of sounds: divine and human, whether near or far. Just as if a man traveling along a highway were to hear the sounds of kettledrums, small drums, conchs, cymbals, and tom-toms. He would know, 'That is the sound of kettledrums, that is the sound of small drums, that is the sound of conchs, that is the sound of cymbals, and that is the sound of tom-toms.' In the same way — with his mind thus concentrated, purified, and bright, unblemished, free from defects, pliant, malleable, steady, and attained to imperturbability — the monk directs and inclines it to the divine ear-element. He hears — by means of the divine ear-element, purified and surpassing the human — both kinds of sounds: divine and human, whether near or far.

"This, too, great king, is a fruit of the contemplative life, visible here and now, more excellent than the previous ones and more sublime.

Source: https://www.accesstoinsight.org/tipitaka/dn/dn.02.0.than.html

Link to PDF Copy of this comprehensive statement of the teachings of the Great Masters of Sant Mat. Dr. Julian Johnson presents an outline of the Yoga of the Audible Life Stream, including an outline of the system of exercises of the Surat Shabd Yoga, the Path of the Masters, used to attain the highest degree of spiritual development.

27th January, 1936. Talk 148.

A Gujerati gentleman said that he was concentrating on sound - nada - and desired to know if the method was right.

M.: Meditation on nada is one of the several approved methods. The adherents claim a very special virtue for the method. According to them it is the easiest and the most direct method. Just as a child is lulled to sleep by lullabies, so nada soothes one to the state of samadhi; again just as a king sends his state musicians to welcome his son on his return from a long journey, so also nada takes the devotee into the Lord’s Abode in a pleasing manner. Nada helps concentration. After it is felt the practice should not be made an end in itself. Nada is not the objective; the subject should firmly be held; otherwise a blank will result. Though the subject is there even in the blank he would not be aware of the cessation of nada of different kinds. In order to be aware even in that blank one must remember his own self. Nada upasana (meditation on sound) is good; it is better if associated with investigation (vichara). In that case the nada is made up of chinmaya and also tanmaya (of Knowledge and of Self). Nada helps concentration.

Yet a few examples of how deep these saints went into the Samadhi associated with the Unstruck Sound.

St John of the Cross

"The heavenly father has uttered only one word: it is his Son. he says it eternally and in an eternal silence. It is in the Silence of the soul that it makes itself heard."

St Teresa of Avila

"As I write this, the noises in my head are so loud that I am beginning to wonder what is going on in it. As I said at the outset, they have been making it almost impossible for me to obey those who commanded me to write. My head sounds just as if it were full of brimming rivers, and then as if all the water in those rivers came suddenly rushing downwards; and a host of little birds seem to be whistling, not in the ears, but in the upper part of the head, where the higher part of the soul is said to be."

Ezekiel 43:3

"I saw the glory of the God of Israel coming from the east. His voice was like the roar of rushing waters, and the land was radiant with his glory."

The Anahata-nadi means the sound made from the prana in the heart chakra. The featuring of chakras in esoteric Buddhism are very prominent and most likely prominent here.

This Pradipika talks about the various sounds that one may hear as the absorption state progresses (meaning the energy moves up various chakras).

Hatha Yoga Pradipika

(69) When the Brahma knot (in the heart) is pierced through by Pranayama, then a sort of happiness is experienced in the vacuum of the heart, and the anahat sounds, like various tinkling sounds of ornaments, are heard in the body.

(72) By this means the Vishnu knot (in the throat) is pierced which is indicated by highest pleasure experienced, And then the Bheri sound (like the beating of a kettle drain) is evolved in the vacuum in the throat.

(73) In the third stage, the sound of a drum is known to arise in the Sunya(space) between the eyebrows, and then the Vayu goes to the Mahasunya, which is the home of all the siddhis.

(75) When the Rudra knot is pierced and the air enters the seat of the Lord (the space between the eyebrows), then the perfect sound like that of a flute is produced.

(84) In the first stage, the sounds are surging, thundering like the beating of kettle drums and jingling ones. In the intermediate stage, they are like those produced by conch, Mridanga, bells, &c.

(85) In the last stage, the sounds resemble those from tinklets, flute, Veena, bee, &c. These various kinds of sounds are heard as being produced in the body.

His Book "Mind Beyond Death"

There are similar practices with sound that lead us to the experience of sound-emptiness. A simple method is given here for tuning in to the natural sound of dharmata, which is always present within our mind but is usually unobserved. The instruction, again, is to begin by assuming a correct posture. When you have settled your mind, you clench your jaws and close your ears to external sounds by plugging your ears with your fingers or pressing your hands against them. This will amplify the basic sound of dharmata and make it more perceptible. It is easiest to hear this sound when it is quiet, particularly at nighttime.

Once you have identified this sound, then you place your awareness on it without wavering. Resting your mind in the sound, you continue to listen, going further and further into the sound itself. The more precise and clear your focus is, the more vivid and sharp the sound becomes. Eventually, your experience of sound deepens to the point that you experience its emptiness, which here is known as the self-sound of the emptiness of dharmata.

This is the same fundamental experience of sound, only in less intense form, which occurs in the bardo of dharmata. As mentioned earlier, because of the acuteness of our senses, sound is so sharp and penetrating at that time that it is compared to the sound of a thousand simultaneous thunderbolts.

It is easier for most of us to understand the emptiness of sound than the emptiness of form. This is because a visual object remains before our eyes for long periods of time, whereas a sound comes and goes. For example, when we read a book, the pages do not disappear as we read them. We can flip back through the book and read each page again. In contrast, when we hear a sound —a voice, a footstep or a whistle—it is gone in the very next moment. We cannot go back to the previous moment and hear it again. Therefore, when we listen to a sound closely, it is like listening to an echo. It conveys the same message of emptiness. That is the practice of the self-sound of the emptiness of dharmata, by which we transcend our mundane experience of sound and leap directly to the realization of sound-emptiness.

Note than Guan-Shi-Yin is translated as "Hearing Worldly Sounds" and is referred to Avalokitesvara or Chenrizig.

Surangama Sutra Chapter 5 on the Ear Organ

Then Guan Shi Yin Bodhisattva arose from his seat, bowed at the Buddha’s feet and said to the Buddha: 5:129

”World Honored One, I remember when, as many kalpas ago as there are sands in the Ganges, here was a Buddha in the world named Contemplating the World’s Sounds. It was under that Buddha that I brought forth the Bodhi-resolve. That Buddha taught me to enter samadhi through a process of hearing and reflecting. 5:134

”Initially, I entered the flow through hearing and forgot objective states. Since the sense-objects and sense-organs were quiet, the two characteristics of movement and stillness crystallized and did not arise. After that, gradually advancing, the hearing and what was heard both disappeared. Once the hearing was ended, there was nothing to rely on, and awareness and the objects of awareness became empty. When the emptiness of awareness reached an ultimate perfection, emptiness and what was being emptied then also ceased to be. Since production and extinction were gone, still extinction was revealed. 5:134

”Suddenly I transcended the mundane and transcendental worlds, and throughout the ten directions a perfect brightness prevailed. I obtained two supreme states. 5:137

”First, I was united above with the fundamental, wonderfully enlightened mind of all the Buddhas of the ten directions, and I gained a strength of compassion equal to that of all the Buddhas, the Thus Come Ones. 5:137

”Second, I was united below with all living beings in the six paths, and I gained a kind regard for all living beings equally. 5:137

”World Honored One, because I served and made offerings to the Thus Come One, Guan Yin, I received from that Thus Come One a transmission of the Vajra Samadhi of all being like an illusion, as one becomes permeated with hearing and cultivates hearing. Because I gained a power of compassion identical with that of all Buddhas, the Thus Come Ones, I became accomplished in thirty-two response-bodies and entered all lands. 5:138

”World Honored One, if there are Bodhisattvas who enter samadhi and vigorously cultivate the extinction of outflows, who have superior understanding and manifest perfected penetration, I will appear in the body of a Buddha and speak dharma for them, causing them to attain liberation. 5:139

”If there are those who are studying, who are tranquil and have wonderful clarity, who are superior and miraculous and manifest perfection, I will appear before them in the body of a Solitarily Enlightened One and speak Dharma for them, causing them to attain liberation. 5:140

[omitted: the other 32 response-bodies]

”This is called the wonderful purity of the thirty-two response-bodies, by which one enters into all lands and accomplishes self-mastery by means of the Samadhi of Becoming Permeated with Hearing and Cultivating Hearing and by means of the miraculous strength of effortlessness. 5:162

”Also, World Honored One, using this Vajra Samadhi of Becoming Permeated with Hearing and Cultivating Hearing, and using the miraculous strength of effortlessness, because I have a kind regard equally for all living beings in the six paths, I go throughout the ten directions and the three periods of time and cause all living beings who encounter bodies of mine to receive the meritorious virtue of fourteen kinds of fearlessness. 5:162

”First: because I do not contemplate sounds for my own sake, but rather listen to the sounds of those whom I contemplate, I can enable living beings throughout the ten directions who are suffering and in distress to attain liberation by contemplating their sounds. 5:163

”Second: since my knowledge and views have turned around and come back, I can make it so that if living beings are caught in a raging fire, the fire will not burn them. 5:164

”Third: since contemplation and listening have turned around and come back, I can make it so that if living beings are floundering in deep water, the water cannot drown them. 5:164

”Fourth: since false thinking is cut off, and my mind is without thoughts of killing or harming, I can make it so that if living beings enter the territory of ghosts, the ghosts cannot harm them. 5:165

”Fifth: since I am permeated with hearing and have brought hearing to accomplishment, so that the six sense-organs have dissolved and returned to become identical with hearing, I can make it so that if living beings are about to be wounded, the knives will break into pieces. I can cause swords of war to have no more effect than if they were to slice into water, or if one were to blow upon light. 5:165

”Sixth: when the hearing permeates and the essence is bright, light pervades the Dharma-realm, so that absolutely no darkness remains. I am then able to make it so that, though yakshas, rakshasas, kumbhandas, pishachas, and putanas may draw near to living beings, the ghosts will not be able to see them. 5:166

”Seventh: when the nature of sound completely melts away and contemplation and hearing return and enter, so that I am separate from false and defiling sense-objects, I am able to make it so that if living beings are confined by cangues and fetters, the locks will not hold them. 5:167

”Eighth: when sound is gone and the hearing is perfected, an all-pervasive power of compassion arises, and I can make it so that if living beings are travelling a dangerous road, thieves will not rob them. 5:168

”Ninth: when one is permeated with hearing, one separates from worldly objects, and forms cannot rob one. Then I can make it so that living beings with a great deal of desire can leave greed and desire far behind. 5:168

”Tenth: when sound is so pure that there is no defiling object, the sense-organ and the external state are perfectly fused, without any complement and without anything complemented. Then I can make it so that living beings who are full of rage and hate will leave all hatred. 5:171

”Eleventh: when the dust has gone and has turned to light, the Dharma realm and the body and mind are like crystal, transparent and unobstructed. Then I can make it so that all dark and dullwitted beings whose natures are obstructed - all atyantikas - are forever free from stupidity and darkness. 5:172

”Twelfth: when matter dissipates and returns to the hearing, then unmoving in the Bodhimanda I can travel through worlds without destroying the appearance of those worlds. I can make offerings to as many Buddhas, Thus Come Ones, as there are fine motes of dust throughout the ten directions. At the side of each Buddha I become a Dharma Prince, and I can make it so that childless living beings throughout the Dharma Realm who wish to have sons, are blessed with meritorious, virtuous, and wise sons. 5:175

”Thirteenth: with perfect penetration of the six sense-organs, the light and what is illumined are not two. Encompassing the ten directions, a great perfect mirror stands in the Empty Treasury of the Thus Come One. I inherit the secret dharma-doors of as many Thus Come Ones as there are fine motes of dust throughout the ten directions. Receiving them without loss, I am able to make it so that childless living beings throughout the Dharma Realm who seek daughters are blessed with lovely daughters who are upright, virtuous, and compliant and whom everyone cherishes and respects. 5:176

”Fourteenth: in this three-thousand-great-thousand world system with its billions of suns and moons, as many Dharma Princes as there are grains of sand in sixty-two Ganges Rivers appear in the world and cultivate the dharma. They act as models in order to teach and transform living beings. They comply with living beings by means of expedients and wisdom, in different ways for each. 5:177

”However, because I have obtained the perfect penetration of the sense-organ and have discovered the wonder of the ear-entrance, after which my body and mind subtly and miraculously included all of the Dharma Realm, I am able to make it so that living beings who uphold my name obtain as much merit and virtue as would be obtained by a person who upheld the names of all those Dharma Princes who are as many as the grains of sand in sixty-two Ganges Rivers. 5:177

”World Honored One, there is no difference between the merit of my one name and the merit of those many other names, because from my cultivation I obtained true and perfect penetration. 5:178

”These are called the fourteen powers of bestowing fearlessness; with them I bless living beings. 5:178

”Moreover, World Honored One, because I obtained perfect penetration and cultivated to certification of the unsurpassed path, I also became endowed with four inconceivable and effortless wonderful virtues. 5:179

”First: as soon as I obtained the miraculous wonder of hearing the mind, the mind became essential and the hearing was forgotten, therefore, there was no distinction between seeing, hearing, sensation, and knowing. I achieved a single, perfect fusion - pure and precious enlightenment. For this reason, I am able to manifest many wonderful appearances and can proclaim boundless secret spiritual mantras. 5:179

”For example, I may make appear one head, three heads, five heads, seven heads, nine heads, eleven heads, and so forth, until there may be a hundred and eight heads, a thousand heads, ten thousand heads, or eighty-four thousand vajra heads; 5:180

”Two arms, four arms, six arms, eight arms, ten arms, twelve arms, fourteen, sixteen, eighteen arms, or twenty arms, twenty-four arms, and so forth until there may be a hundred and eight arms, a thousand arms, ten thousand arms, or eighty-four thousand mudra arms; 5:180

”Two eyes, three eyes, four eyes, nine eyes, and so forth until there may be a hundred and eight eyes, a thousand eyes, ten thousand eyes, or eighty-four thousand pure and precious eyes, sometimes compassionate, sometimes awesome, sometimes in samadhi, sometimes displaying wisdom to rescue and protect living beings so that they may attain great self-mastery. 5:181

”Second: because of hearing and consideration, I escaped the six defiling objects, just as a sound leaps over a wall without hindrance. And so I have the wonderful ability to manifest shape after shape and to recite mantra upon mantra. These shapes and these mantras dispel the fears of living beings. Therefore, throughout the ten directions, in as many lands as there are fine motes of dust, I am known as one who bestows fearlessness. 5:181

”Third: because I cultivated fundamental, wonderful, perfect penetration and purified the sense-organ, everywhere I go in any world I can make it so that living beings renounce their physical and material valuables to seek my sympathy. 5:182

”Fourth: I obtained the Buddhas’ mind and was certified as having attained the ultimate end, and so I can make offerings of rare treasures to the Thus Come Ones of the ten directions and to living beings in the six paths throughout the Dharma Realm. 5:183

”If they seek a spouse, they obtain a spouse. If they seek children, they can have children. Seeking samadhi, they obtain samadhi; seeking long life, they obtain long life, and so forth to the extent that if they seek the great Nirvana, they obtain great Nirvana. 5:183

”The Buddha asks about perfect penetration. From the gateway of the ear, I obtained a perfect and illumining samadhi. The conditioned mind was at ease, and therefore I entered the appearance of the flow, and obtaining samadhi, I accomplished Bodhi. This is the foremost method. 5:184

”World Honored One, that Buddha, the Thus Come One, praised me as having obtained well the dharma-door of perfect penetration. In the great assembly he bestowed a prediction upon me and the name, Guan Shi Yin. 5:184

”Because my contemplation and listening is perfectly clear throughout the ten directions, the name Guan Shi Yin pervades all the realms of the ten directions.” 5:185

(Reviving the archived post)

The Hatha Yoga Pradipika is explicit about the significance of hearing the Unstruck Sound:

4:65 "Âdinâtha propounded 1¼ crore methods of trance, and they are all extant. Of these, the hearing of the anâhata nâda is the Only one, the chief, in my opinion."

I have been a Yoga practitioner for about 10 years and was given the gift of hearing the Nada during my daily Pranayama (breathing) practice this year. Pranayama purifies the Nadis (Energy Channels); this is the normal progression:

2:78 "When the body becomes lean, the face glows with delight, Anâhatanâda manifests, and eyes are clear, body is healthy, bindu under control, and appetite increases, then one should know that the Nâdîs are purified and success in Haṭha Yoga is approaching."

There is quite a bit of information about the history of the practice, its benefits and getting to the point of hearing the Unstruck Sound, but I have found very little guidance on the practice itself. My Teacher explained it is a very personal journey for those who reach this level. And to approach listening to the Anahata Nada with humble gratefulness.

As a side note, there seems to be some confusion between the Anahata Nada and tinnitus. As I understand it, tinnitus is an incessant and uncontrollable irritation, making it a difficult focus for meditation. By comparison, the Unstruck Sound is irresistible and pleasant to listen, and takes effort to perceive.