The immediate effects of the frequency and sound pressure levels of short-duration noise on sleep stages

It has been established that noise during sleep is associated with various health risks, and Night Noise Guidelines for Europe define awakening thresholds based on individual noise events. However, previous studies have mainly focused on the effects of various types of traffic noise and on evaluating overall sleep quality across the entire night and have not clarified how different acoustic characteristics influence sleep or how noise exposure immediately affects sleep stages. Therefore, we conducted a sleep experiment with 30 participants and they were exposed to 3-s chirp sounds at 65 and 50 dB during sleep. First, to examine the effects of noise exposure, we compared sleep stage recordings between the nights with and without sound presentation. As a result, an increase in the number of awakenings was observed following sound presentation. Next, to clarify the immediate effects of sounds on sleep, we compared the rate of change in sleep stage before and after sound presentation. From this analysis, higher sound pressure levels were more likely to induce change in sleep depth. In contrast, no significant differences were observed based on frequency.