Beatline
The research
A binaural beats glossary, A to Z
15 August 2026
This field runs on borrowed vocabulary. Words from acoustics, EEG research and psychotherapy get used interchangeably by people selling recordings, and the borrowing is where most of the confusion comes from.
Here is every term you are likely to meet, defined plainly. Where a word carries a claim the evidence does not support, it says so.
A
Alpha - The EEG band from 8 to 13 Hz, associated with relaxed wakefulness. A real naming convention from brain research. It becomes a claim only when someone tells you that playing an 8 Hz beat produces that state, which is the part that is contested.
Ambient - Recorded sound rather than generated tone: rain, fire, surf. Filed separately here because it works by masking rather than by any beat mechanism, and the evidence behind it is considerably stronger.
Auditory beat stimulation - The umbrella term for binaural beats, isochronic tones and their relatives. Useful when you want to talk about the family rather than pick a member.
B
Beat frequency - The difference between the two tones, and the number the whole field is named for. Play 200 Hz and 203 Hz and the beat frequency is 3 Hz.
Beta - The EEG band from 13 to 30 Hz, associated with alert, active thinking. Same caveat as alpha: the band is real, the promise attached to it is the claim.
Bilateral stimulation - Sound alternating between the ears, left to right and back. Comes out of EMDR, a trauma therapy, and is not a variant of binaural beats despite the superficial resemblance.
Binaural beat - A pulse you perceive when each ear receives a slightly different steady tone. It is not present in either ear and not present in the air. Your auditory system constructs it.
Brown noise - Noise whose power drops 6 dB per octave, producing a deep rumble. Named for Brownian motion, not the colour.
C
Carrier frequency - The pitch the beat rides on. For a 3 Hz beat you might use carriers of 200 and 203 Hz; the carrier is 200, the beat is 3. Carrier choice appears to matter more than most charts admit: the one gamma study with EEG-confirmed entrainment found the effect varied by carrier.
D
Delta - The EEG band from 0.5 to 4 Hz, associated with deep sleep. The one band where a specific rate has a specific result behind it: a 3 Hz beat produced more delta activity and longer stage N3 in one small experiment.
E
EEG - Electroencephalography. Electrodes on the scalp measuring electrical activity. Every band name in this glossary comes from EEG research, which is why the names are real even where the claims are not.
Effect size - How big a finding is, as distinct from whether it is statistically significant. Usually reported as g or d, where roughly 0.2 is small, 0.5 medium and 0.8 large. The pooled figure for binaural beats is g = 0.45.
Entrainment - The claim that your brain will synchronise its activity to an external rhythm. This is the mechanism nearly every binaural beats product assumes, and 8 of 14 studies contradicted it. The single most important word on this page.
F
Frequency following response - Another name for entrainment. Same claim, same problem.
G
Gamma - The EEG band above 30 Hz, associated with alert processing. The most interesting open thread in the field: one 2025 study of 80 students found improved attention with EEG-confirmed entrainment, varying by carrier. Still exploratory.
Grey noise - Noise shaped to sound flat to human hearing rather than flat on a meter, correcting for the fact that your ears are not neutral.
H
Heterogeneity - How much the studies in a review disagree with each other, usually reported as I². Above 75% is conventionally "considerable". The binaural anxiety literature hits 91.6%, which means the studies are barely measuring the same thing and the average tells you less than its size suggests.
I
Isochronic tone - A single tone switched rapidly on and off. The pulse is physically in the sound, so unlike a binaural beat it works on a speaker. Also barely studied: only 2 of 17 studies in the main entrainment review used them.
M
Masking - Raising the background sound level so a sudden noise no longer stands out. Unglamorous, well understood, and the best-supported mechanism in this entire app.
Meta-analysis - Pooling results from many studies into one estimate. More reliable than any single trial, and only as good as the studies inside it, which is why heterogeneity matters.
N
Noise colour - A name for the slope of a sound's power spectral density. White, pink, brown, blue, violet, grey and green each describe a measurable distribution, not a mood.
P
Pink noise - Noise dropping 3 dB per octave, which cancels the doubling of hertz per octave and sounds even to the ear. The distribution natural broadband sound tends toward.
Power spectral density - How a sound's energy is distributed across frequencies. The thing the noise colours are named for.
Pure tone - A single frequency with no harmonics. What a solfeggio "frequency" actually is.
S
Solfeggio frequencies - A set of specific pitches, 528 Hz and 432 Hz among them, said to have particular effects. Attributed to a mediaeval hymn rather than to any measurement, and the larger trial found anxiety fell in every arm including no music at all.
Superior olivary complex - The part of the brainstem where signals from both ears first meet, and where a binaural beat is assembled. The one piece of mechanism in this glossary that nobody disputes.
T
Theta - The EEG band from 4 to 8 Hz, associated with drowsiness and some meditative states. A 6 Hz beat produced more theta in one experiment, including frontal-midline theta associated with focused attention - an EEG resemblance, which is not the same as the state itself.
W
White noise - Equal power at every frequency. Sounds hissy and bright rather than neutral, because human hearing groups frequencies into octaves and the top octave contains far more of the energy.
The pattern worth noticing
Read the list back and a shape appears. The terms describing what a sound physically is - carrier, beat frequency, power spectral density, noise colour — are precise and uncontested. So is the one anatomical term, the superior olivary complex.
The terms describing what a sound does to you are where it gets thin. Entrainment is contested. The band-to-mood mappings were borrowed from descriptions of brain states and reattached to beat rates. The solfeggio numbers were never measured at all.
That is not a reason to avoid the field. It is a reason to notice which kind of word you are being sold.