Study on the Effects of Infra- and Low Frequency Sound on the Sleep by EEG Recording

This study was performed to investigate the effects of infra- and low frequency sound on sleep. Healthy students were periodically exposed to sound stimuli with frequencies of 10, 20, 40 and 63 Hz throughout their sleep while EEG was continuously recorded. The effects were evaluated by the reaction rate and the changes of sleep pattern which consisted of the sleep efficiency index, numbers of changes in sleep stage and the proportion of each sleep stage to time in bed.

The reaction rate was highest in sleep stage 1 and lowest in sleep stages 3 & 4. As concerns the exposures at sound pressure levels under 85 dB, there were no significant differences in the reaction rates for the four frequencies used. On the other hand, for sound pressure levels over 85 dB, the reaction rates observed at 40 and 63 Hz were significantly higher than those observed at 10 and 20 Hz. The sleep pattern was not significantly affected by exposure to the sounds used in this experiment.