Reference

Sound Therapy Glossary

A plain-English glossary of sound therapy, binaural beat, and acoustic medicine terms.

A

Adaptive soundscape

An adaptive soundscape is generative audio that changes in real time in response to signals such as time of day, activity, or biometric input, rather than playing a fixed track.

Alpha waves

Alpha waves are brain waves of about 8 to 12 Hz on an EEG. They are strongest during relaxed, wakeful states (often with the eyes closed) and were the first human brain rhythm recorded.

Auditory cortex

The auditory cortex is the part of the brain's temporal lobe that processes sound. It is organised by frequency (tonotopically) and turns incoming acoustic signals into what we perceive as hearing.

B

Binaural beats

Binaural beats are an auditory illusion: play two slightly different tones, one in each ear, and the brain perceives a third "beat" at the difference frequency. Headphones required.

Brainwave entrainment

Brainwave entrainment is the idea that rhythmic audio or visual stimulation can nudge brain-wave activity toward a target frequency. Effects are studied but evidence is mixed.

Brown noise

Brown noise (Brownian noise) has more energy at low frequencies, giving a deeper rumble than white noise. It is popular for focus and sleep, with mostly anecdotal support.

D

Delta waves

Delta waves are the slowest brain waves, roughly 0.5 to 4 Hz on an EEG. They dominate the deepest stage of sleep (slow-wave sleep) and are linked to physical restoration.

G

Gamma waves are fast brain waves above about 30 Hz on an EEG, often discussed around 40 Hz. They are linked to attention and neural synchrony; brain-health claims around them are still being researched.

I

Isochronic tones

Isochronic tones are single tones pulsed rapidly on and off at a set rate. Unlike binaural beats, they work through speakers and need no headphones, and are used in brainwave-entrainment audio.

N

Notched sound therapy

Notched sound therapy is an experimental approach that removes a band of frequencies around a person's tinnitus pitch from music or noise. Evidence is mixed; it is not a guaranteed treatment.

P

Pink noise

Pink noise has equal energy per octave, so it sounds softer and more balanced than white noise. Some small sleep studies have looked at it, with early and limited results.

Polyvagal theory

Polyvagal theory, proposed by Stephen Porges, links the vagus nerve to how we respond to safety and threat. It is influential in therapy but its core claims remain scientifically debated.

Psychoacoustics

Psychoacoustics is the science of how people perceive sound: how the ear and brain turn acoustic signals into experiences of loudness, pitch, and location. It underpins everything from audio codecs to sound therapy.

S

Solfeggio frequencies

The Solfeggio frequencies are a set of nine tones (174 to 963 Hz) popularised by a 20th-century revival and associated with various claimed effects. The benefit claims are not clinically proven.

Sound bath

A sound bath is a group or solo relaxation session in which you lie down and listen to sustained tones from instruments such as gongs or singing bowls. It is a relaxation practice.

Sound healing

Sound healing (used interchangeably with sound therapy) is the use of tones, music, or vibration to support relaxation and wellbeing. Evidence for specific frequency effects is limited.

T

Theta waves

Theta waves are brain waves of about 4 to 8 Hz on an EEG. They appear during drowsiness, light sleep, and some meditative states, and are studied in relation to memory.

Tinnitus retraining therapy

Tinnitus retraining therapy (TRT) is a structured clinical programme combining counselling with sound enrichment, aimed at habituation to tinnitus rather than removing it. It is delivered by trained clinicians.

V

Vagal tone

Vagal tone is the activity of the vagus nerve on the heart, often estimated from heart rate variability. Higher resting vagal tone is linked to calmer, more flexible autonomic regulation.

Voice analysis

Voice analysis is the computational study of speech acoustics (pitch, timing, quality) to infer states such as stress or mood. It is an emerging research area, not a diagnostic tool.

W

White noise

White noise is a signal with equal energy across all audible frequencies, heard as a steady hiss. It is widely used to mask disruptive sounds for sleep and focus.

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