Musicians Engineers & Schools. Study the Psychoacoustic…


Psychoacoustics is the scientific study of sound perception. More specifically, it is the branch of science studying the psychological and physiological responses associated with sound (including noise, speech and music). It can be further categorized as a branch of psychophysics. Psychoacoustics received its name from a field within psychology—i.e., recognition science—which deals with all kinds of human perceptions. It is an interdisciplinary field of many areas, including psychology, acoustics, electronic engineering, physics, biology, physiology, and computer science.[1]

Limits of perception[edit]

An equal-loudness contour. Note peak sensitivity around 2–4 kHz, the frequency around which the human voice centers.

The human ear can nominally hear sounds in the range 20 Hz (0.02 kHz) to 20,000 Hz (20 kHz). The upper limit tends to decrease with age; most adults are unable to hear above 16 kHz. The lowest frequency that has been identified as a musical tone is 12 Hz under ideal laboratory conditions.[6] Tones between 4 and 16 Hz can be perceived via the body’s sense of touch.

Psychoacoustics Part 2 : is essentially the study of the perception of sound. This includes how we listen, our psychological responses, and the physiological impact of music and sound on the human nervous system.
In the realm of psychoacoustics, the terms music, sound, frequency, and vibration are interchangeable, because they are different approximations of the same essence. The study of psychoacoustics dissects the listening experience.

Traditionally, psychoacoustics is broadly defined as “pertaining to the perception of sound and the production of speech.” The abundant research that has been done in the field has focused primarily on the exploration of speech and of the psychological effects of music therapy. Currently, however, there is renewed interest in sound as vibration.

An important distinction is the difference between a psychological and a neurological perception. A song or melody associated with childhood, a teenage romance, or some peak emotional experience creates a memory-based psychological reaction. There is also a physiological response to sounds, however. Slightly detuned tones can cause brain waves to speed up or slow down, for instance. Additionally, soundtracks that are filtered and gated (this is a sophisticated engineering process) create a random sonic event. It triggers an active listening response and thus tonifies the auditory mechanism, including the tiny muscles of the middle ear. As a result, sounds are perceived more accurately, and speech and communication skills improve. While a psychological response may occur with filtered and gated sounds, or detuned tones, the primary effect is physiological, or neurological, in nature.

Research on the neurological component of sound is currently attracting many to the field of psychoacoustics. A growing school of thought — based on the teachings of the Dr. Alfred Tomatis — values the examination of both neurological and psychological effects of resonance and frequencies on the human body.

Thanks to the ground breaking findings of Dr. Tomatis (1920-2001), we have come to understand the extraordinary power of the ear. In addition to its critical functions of communication and balance, the ear’s primary purpose is to recycle sound and so recharge our inner batteries. According to Tomatis, the ear’s first function in utero is to govern the growth of the rest of the physical organism. After birth, sound is to the nervous system what food is to our physical bodies: Food provides nourishment at the cellular level of the organism, and sound feeds us the electrical impulses that charge the neocortex. Indeed, psychoacoustics cannot be described at all without reference to the man known as the “Einstein of the ear.”

In the realm of application-specific music and sound, psychoacoustically-designed soundtracks revolve around the following concepts and techniques:

  • Intentionality (focused application for specific benefit)
  • Resonance (tone)
  • Entrainment (rhythm)
  • Pattern Identification (active listening or passive hearing)
  • Sonic Neurotechnologies (highly specialized sound processing)

Resonance & Entrainment
Consider the following: Anything that moves has a vibration. Though invisible, every aspect of our material world at the atomic level moves constantly. Wherever there is motion, there is frequency. Though inaudible at times, all frequencies make a sound. All sounds resonate and can affect one another. In the spectrum of sound — from the movement of atomic particles to the sensory phenomenon we call music — there is a chain of vibration:

  • All atomic matter vibrates.
  • Frequency is the speed at which matter vibrates.
  • The frequency of vibration creates sound (sometimes inaudible).
  • Sounds can be molded into music.

This chain explains the omnipresence of sound.

Resonance is the single most important concept in understanding the constructive or destructive role of sound in your life. Entrainment, sympathetic vibration, resonant frequencies, and resonant systems all fall under the rubric of resonance. Resonance can be broadly defined as “the impact of one vibration on another.” Literally, it means “to send again, to echo.” To resonate is to “re-sound.” Something external sets something else into motion, or changes its vibratory rate. This can have many different effects — some subtle and some not so.

From iceburgs to airport construction to the human body, soundwaves have the capacity to alter, to actually shift frequency. Simply put, sound is a powerful — yet often ignored — medium for change.

Another fascinating and important aspect of resonance is the process of entrainment. Entrainment, in the context of psychoacoustics, concerns changing the rate of brain waves, breaths, or heartbeats from one speed to another through exposure to external, periodic rhythms.

The most common example of entrainment is tapping your feet to the external rhythm of music. Just try keeping your foot or your head still when you are around fun, up-tempo rhythms. You will see that it is almost an involuntary motor response. However, tapping your feet or bopping your head to external rhythms is just the tip of the iceberg. While your feet might be jitterbugging, your nervous system may be getting a terrible case of the jitters!

Rhythmic entrainment is contagious: If the brain doesn’t resonate with a rhythm, neither will the breath or heart rate. In this context, rhythm takes on new meanings. Not only is it entertaining, but rhythmic entrainment is a potent sonic tool as well — be it for motor function or other autonomic processes such as brainwave, heart, and breath rates. Alter one pulse (such as brain waves) with music, and the other major pulses (heart and breath) will dutifully follow.

When it comes to the intentional applications of music, the entrainment effect completes the circle of the chain of vibration: Atomic matter —> vibration —> frequency —> sound —> sympathetic vibration (resonance) —> entrainment.

Music alters the performance of the nervous system primarily because of entrainment. Entrainment is the rhythmic manifestation of resonance. With entrainment, a stronger external pulse does not just activate another pulse but actually causes the latter to move out of its own resonant frequency to match it.

Understanding the interlocking concepts of resonance and entrainment enables us to grasp the way external tone and rhythm can heal or create havoc. Sound affects glass and concrete as well as brain waves, motor response, and organic cells.

Pattern Identification
Simply put, pattern identification is one of the brain’s analytical processes. Identifying a pattern (visual, auditory, odiferous, kinesthetic) enables cerebral attention to shift from active awareness to passive acknowledgement. Listening and looking are active functions; hearing and seeing are passive.

In active listening mode, the middle ear function is highly engaged while the brain seeks to identify a pattern. Once an auditory pattern is found, passive hearing begins. Habituation sets in and the brain focuses on other things. There are specific times when active listening or passive hearing is preferable. Active listening stimulates the nervous system. Passive hearing is neutral or “discharging.”

Sonic Neuro-Technologies
Representing two distinct approaches to therapeutic sound, filtration/gating (F/G) and binaural beat frequencies (BBFs) currently define the growing field of “sonic neurotechnologies.” This phrase was coined by Joshua Leeds to describe the arena of soundwork that depends on the precise mechanical manipulation of soundwaves to bring about desired changes in the psyche and physical body. Two diverse approaches to the processing of sound frequencies hold great interest and are used on some of the audio programs in Sound Remedies.

Filtration/gating (F/G) techniques have been honed in Tomatis clinics worldwide. By gradually gating and filtering out the lower range of music (sometimes up to 8000 Hz), and then adding the frequencies back in, a retraining of the auditory processing system occurs. The effects of filtration and gating are felt on a psychological, neurodevelopmental, and physical level. The application of sound stimulation has been effective in the remediation of many neurodevelopmental issues. Children and adults with learning/attention difficulties, developmental delays, auditory processing problems, sensory integration and perceptual challenges have experienced profound improvement.

Another approach to sound processing is the field of binaural beat frequencies (BBFs). By listening through stereo headphones to slightly detuned tones (i.e., sound frequencies that differ by a prescribed number of Hz), sonic brainwave entrainment takes place. Facilitating a specific range of brainwave states may assist in arenas such as pain reduction, enhanced creativity, or accelerated learning.

These two sonic neurotechnologies — used separately — have roots in neurology, physiology, and psychology. They must be used carefully and wisely. BBF and F/G soundtracks can be powerful tools. Consequently, proper consideration must always be afforded.

Please note: Sound products with BBFs or F/G contribute to health and wellness, but they are never intended to replace medical diagnosis or treatment. Do not drive or operate machinery while listening to sound programs that use these methedologies.

The therapeutic use of sound, like any new tool, requires discipline, education, and strict observance of ethical standards. There is currently no established licensure in the use of sonic neurotechnologies. Therefore the onus of responsibility for handling the changes that occur as a consequence of the application of these methods (most specifically, filtration/gating) falls on the practitioner. Sound is a marvelous adjunct to an existing profession. Therapists and educators will do well in performing due diligence and acquiring proper training.

Sound Stimulation with Filtration/Gating
In the broadest definition, sound stimulation can be defined as the excitement of the nervous system by auditory information. Sound stimulation auditory retraining narrows the focus. In this context, a precise application of electronically processed sound, through headphones, can have the effect of retraining the auditory mechanism to take in a wider spectrum of sound frequencies. An ear that cannot process tone properly is a problem of great magnitude. As discussed in previous chapters, sufficient auditory tonal processing is a prerequisite to normal auditory sequential processing.

  • Auditory tonal processing (ATP) may be defined as the ability to differentiate between the tones utilized in language.
  • Auditory sequential processing (ASP) is the ability to link pieces of auditory information together.

Auditory tonal processing is a basis for more complex levels of auditory sequential processing. ASP is the ability to receive, hold, process, and utilize auditory information using our short-term memory. As the foundation for short-term memory, ASP is one of the building blocks of thinking.

Sequential processing functions are fundamental to speech, language, learning, and other perceptual skills. The ability to interpret sound efficiently provides the neurological foundation for these sequential functions. Per neurodevelopmental specialist Robert J. Doman Jr., “many people who have experienced auditory processing deficits have seen their sequential functions return and/or improve when proper tonal processing is restored.”

The primary sound application used in the remediation of impaired tonal processing was created by Alfred Tomatis. Further discussions cannot take place without absolute acknowledgment of his pioneering research. The current field of sound stimulation auditory retraining evolves from Tomatis’s discoveries of the powerful effect of filtration and gating of sound.

In the context of auditory retraining, let’s summarize these terms:

  • Filtration means the removal of specific frequencies from an existing sound recording, be that the music of Mozart or a recording of a voice. Through the use of sound processing equipment, it is possible to isolate and mute certain frequency bandwidths. With filtration, any part of the low, mid, or high end of a recording can be withdrawn and reintroduced at will. On a visual level, imagine erasing the bottom part of a picture and then eventually drawing it back in. This is filtration.
  • Gating refers to the creation of a random sonic event. This is accomplished by electronically processing a soundtrack so it unexpectedly jumps between the high and low frequencies. While not always pretty to listen to, the net effect of this sound treatment is an extensive exercising of the muscles of the middle ear. The combined process of filtration and gating creates a powerful auditory workout. And for good reason! The middle ear mechanism must work very hard to translate the complexity of the “treated” incoming sound.


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