Psychophysiological acoustics of indoor sound due to traffic noise during sleep

Abstract

The relation between the physical characteristics of sound and an individual's perception of its as annoyance is complex and unclear. Sleep disturbance by sound is manifested in the physiological responses to the sound stimuli and the quality of sleep perceived in the morning. Both may result in deterioration of functioning during wakefulness. Therefore, psychophysiological responses to noise during sleep should be studied for the evaluation of the efficacy of sound insulation. Nocturnal sleep and indoor sound level were recorded in the homes of 12 subjects living along a highway with high traffic density. Double glazing sound insulation was used to create two experimental conditions: low insulation and high insulation. Twenty recordings were made per subject, ten recordings in each condition. During the nights with low insulation the quality of sleep was so low that both performance and mood were negatively affected. The enhancement of sound insulation was not effective enough to increase the restorative effects of sleep. The transient and peaky characteristics of traffic sound were also found to result in non-adaptive physiological responses during sleep. Sound insulation did have an effect on noise peak characteristics such as peak level, peak duration and slope. However, the number of sound peaks were found to be the same in both conditions. The relation of these sound peaks detected in the indoor recorded sound level signal to characteristics of passing vehicles was established, indicating that the sound peaks causing the psychophysiological disturbances during sleep were generated by the passing vehicles. Evidence is presented to show that the reduction in sound level is not a good measure of efficacy of sound insulation. The parameters of the sound peaks, as described in this paper, are a better representation of psychophysiological efficacy of sound insulation.