Rhythmic waves in the electroencephalogram that have a smaller amplitude than alpha waves and have an average frequency of about 25 cps.

EEG frequency in the range of 13-35 Hz; when the predominant frequency, beta rhythm is usually associated with alert wakefulness or vigilance and is accompanied by a high tonic EMG.

The dominant pattern (14 to 25 cps) of brain waves found in an alert adult responding to a stimulus.