Brainwave bands explained: delta to gamma

Brainwave bands describe ranges of electrical activity measured with EEG. They are not audible pitches or five mutually exclusive modes of mind. A recording can contain several rhythms at once, and interpretation depends on where and when activity is measured. The familiar frequency labels also appear on binaural audio, where they describe the difference between carrier tones.

Delta Waves Explained: The 0.5-4 Hz EEG Band

Delta is commonly placed around 0.5–4 Hz. Slow-wave activity is prominent in deep non-REM sleep, which is one reason the name appears on sleep-audio charts. NHLBI's sleep-stage guide explains the distinction between deep non-REM and other stages.

For reading a waveform, 1 Hz means one cycle per second; 0.5 Hz takes two seconds per cycle. A delta-labeled audio track instead uses a small difference between much higher audible carriers.

Theta Waves Explained: The 4-8 Hz EEG Band

Theta commonly spans about 4–8 Hz. Slower rhythms become more prominent during drowsiness and early sleep. The American Epilepsy Society EEG atlas describes how background rhythms change with wakefulness and drowsiness.

At 6 Hz, six cycles fit into a second. In binaural audio, a 6 Hz setting refers to the gap between the two carriers. It is not a separate 6 Hz note in the headphones. If you choose a theta-labeled sound for meditation, judge whether it is a comfortable attention anchor.

Alpha Waves Explained: The 8-13 Hz EEG Band

Alpha is commonly charted around 8–13 Hz. A familiar posterior alpha rhythm appears during relaxed eyes-closed wakefulness and changes when the eyes open. Location and reactivity matter as well as frequency; the EEG atlas explains that context.

The audio label uses the same numeric range for another purpose. Two carriers separated by 10 Hz are an alpha-rate binaural example, regardless of whether their audible pitch is relatively low or high. You can use the number to reproduce a setting.

Beta Waves Explained: The 13-30 Hz EEG Band

Beta is often defined as roughly 13–30 Hz. It appears in normal waking EEG, including frontal and central regions, and is interpreted alongside other features of the recording. The EEG atlas describes low-amplitude beta in waking background activity.

Twenty cycles per second is a beta-range rate; two audible carriers 20 Hz apart give the corresponding binaural difference. If you compare a faster beat while working, keep the level low and measure something ordinary, such as whether you finish the intended task without the sound competing for attention.

Gamma Waves Explained: EEG Activity Above 30 Hz

Gamma is a broad label above about 30 Hz; the upper boundary depends on the study and measurement. Fast activity also demands careful separation from non-neural signals such as muscle activity. Research may investigate narrow gamma ranges rather than treating all high-frequency activity as one thing. A review of EEG responses to binaural stimulation discusses inconsistent results across studied bands.

A 40 Hz audio label needs a second question: does it name a pure tone, amplitude modulation or the difference between two carriers? Those signals are physically different. Read the pure-tone guide before transferring a finding from one kind of 40 Hz stimulation to another.

Try your next listening session in Biaura

Biaura is an iPhone sound app with binaural beats, colored noise, pure tones and ambient sounds. Choose one sound, adjust it to a comfortable level, and set a session timer. Explore the sound library or use the download button below to open the App Store.