Laboratory studies of a sound system that maintains wakefulness.

Two studies investigated the effects of a waking sound that enhances wakefulness. Study I investigated the effect of the sound level and Study 2 the effect of time and frequency variability of the sound. The recordings of EEG and subjective ratings were analysed to study the effect upon wakefulness. The waking effect increased when sound varied in duration and frequency. A number of specific conditions necessary for the waking effect are described. The exposure should be based on high frequency sounds and several tones chosen to produce disharmony. The exposure should be loud enough to be heard over the masking background noise. The duration and tonal quality should be variable from one presentation to another.