The frequency of EEG waves is devided into 4 groups or frequency bands, namely:

• delta frequency band: under 4 Hz;
• theta frequency band: from 4 to under 8 Hz;
• alpha frequency band: from 8 to 13 Hz;
• beta frequency band: over 13 Hz.

References:

1. Brain Wave Frequencies in Crossroads Institute. (Hits: 867 - Rating: 0 - Votes: 0) Rate/Review It!

2. Primer of Eeg With a Mini-Atlas by A. James Rowan and Eugene Tolunsky, available from amazon.com. (Hits: 799 - Rating: 0 - Votes: 0) Rate/Review It!