The feedback consists of two environmental tones signaling the general range of the client's state-of-relaxation, and tones that signal momentary bursts of EEG in one or the other reward band. The alpha environment (trace 3) is a running stream, and its tone is a high-pitched bell. The theta environment (trace 2) is ocean waves, and the theta tone is a low-pitched bell. As relaxation deepens, the ongoing environmental sound will cross-fade from stream to ocean and low-pitched bell tones will replace the high-pitched tones. In cases where both frequency ranges are over threshold at the same time, the system is biased toward signaling the trace 2 state. If the unbiased option was selected in game tailoring, the trace with the highest above-threshold value is selected.
In short, alpha-theta is designed to transition from the stream to the ocean sounds. When the session starts you will hear the stream and higher-pitched bells with extended periods of alpha in excess of the threshold. As the theta begins to predominate and exceed its threshold you will hear the ocean and lower pitched bells. If both alpha and theta are in excess of their thresholds, the default behavior is to play the ocean sound.
You also have additional control over the volume and rate of change between sounds by pressing the "v" key during a session. Here is a description of these controls:
- The default volume levels for the background sounds and reward tones are set to a percentage value.
- Theta (ocean wave) volume
- Alpha (babbling brook) volume
- Alpha reward (Bell) volume
- Theta reward (Gong) volume
The next-to-last option adjusts the master volume. The last option adjusts the fade or rate-of-change speed used when switching between the wave and babble sounds. The Edge rate border controls the percentage of range (near the edges of the transition) where a double fade rate change will be used.
At the bottom of the Alpha-Theta display are the "names" of the sounds along with the relative percentage of the two signals (alpha and theta). When a tone is generated, the appropriate "name" for the tone displays during the playing of the tone. The "Step" value is the current setting of the fade step value which controls how rapidly the environmental sounds transition.