Alpha waves

Alpha waves are brain waves with a frequency of about 8 to 12 Hz. Frequency here is measured in hertz (Hz), the number of cycles a second, so 8 to 12 Hz means roughly eight to twelve cycles each second. These waves are read using EEG (electroencephalography), a painless test that records the brain's electrical activity through small sensors on the scalp. Alpha is most prominent during relaxed wakefulness, especially when the eyes are closed and the mind is not working on a task, and it is strongest over the back of the head (the occipital region).¹ They were the first human brain rhythm described, recorded by the German neurologist Hans Berger in the 1920s, which is why alpha is sometimes called the Berger rhythm. On EEG, "the posterior dominant alpha rhythm (8-12 Hz)" is a normal feature of the awake brain.²

EEG bands are simply named ranges of brain-wave speed. From slowest to fastest, the common labels are delta (about 0.5 to 4 Hz), theta (about 4 to 8 Hz), alpha (about 8 to 12 Hz), beta (about 12 to 30 Hz), and gamma (above about 30 Hz). Alpha sits in the middle, between the drowsier theta band and the alert, busy beta band, so its presence tends to signal a calm but awake state. A telling feature is that alpha typically fades when the eyes open or the brain takes on a task; this drop is called alpha blocking or desynchronisation, and the posterior alpha rhythm "is typically attenuated by eye opening and mental effort".²

On the evidence, honesty matters. Some audio products claim to "boost" alpha, usually through binaural beats or isochronic tones, for calm or focus. Rhythmic sound really can produce a matching rhythm in the hearing parts of the brain, a well-measured effect called the frequency-following response.³ But whether listening reliably raises alpha or shifts the wider brain into an alpha state is modest and mixed; a systematic review found the studies inconsistent, with no clear trend either way.⁴ Treat any "alpha wave" track as relaxing background sound, not a guaranteed way to change your brain state.