Sleep disturbances due to exposure to tone pulses throughout the night

Sleep electroencephalograms (EEGs) and subjective reports data were obtained from six subjects (male college students) during 2 nights of baseline observation and 5 experimental nights of exposure to a 90-100 dB, 25 ms, 1,000 c/s tone pulse with various interstimulus intervals. The first of the 5 experimental nights started with an intertone interval of 80 s. On each of the following 4 nights, the intertone interval was fixed at 40-, 10-, 2.5-, or 1-s intervals, respectively. With the intensification of noise stimulus by shortening the intervals of tone pulses, a progressive disruption of nightly EEG sleep patterns was observed as follows: (a) increased frequency of awakenings and sleep stage changes during the night, (b) prolonged sleep latency, and (c) increased percentage of time spent in stage 1 sleep. However, total sleep time, REM latency, inter-REM intervals, and the percentages of time in stages 2, 3, 4, and REM sleep did not change significantly. The degree of subjective sleep disturbance was highly associated with objective measures of nightly EEG sleep patterns.