Effect of the frequency spectrum of road traffic noise on sleep: A polysomnographic study.

Spectrum of sound affects noise annoyance. Spectral differences of road traffic noise (RTN) transmitted indoors are usual because of spectrally different sound insulation of facades. The purpose was to compare the effect of RTN spectrum on sleep. Twenty-one volunteers slept three nights in a sleep laboratory in three sound conditions: low-frequency (LF) RTN, high-frequency (HF) RTN, and quiet (control). The A-weighted equivalent levels were 37, 37, and 17 dB LAeq,8h, respectively. The nocturnal time profiles of LF and HF were equal. Sleep was measured with polysomnography and questionnaires. HF and LF did not differ from each other in respect to their effects on both objective and subjective sleep quality. The duration of deep sleep was shorter, satisfaction with sleep lower, and subjective sleep latency higher in HF and LF than in quiet. Contrary to subjective ratings given right after the slept night, HF was rated as the most disturbing condition for sleep after the whole experiment (retrospective rating). The finding suggests the sound insulation spectrum of the facade construction might play a role regarding the effects of RTN. More research is needed about the effects of spectrum on sleep because the field is very little investigated.

Subjective and objective rating of the sound insulation of residential building façades against road traffic noise.

Sound insulation in a building façade plays a key role in the control of road-traffic noise. Façade performance can be described using various internationally standardized single-number quantities (SNQs) with different frequency weightings. The purpose of this study was to evaluate how 25 different SNQs explain the subjective ratings of spectrally different road-traffic sounds transmitted through a façade. Forty-three participants took part in a psychoacoustic laboratory experiment. The task was to evaluate five spectrally different road-traffic sound types transmitted through 12 simulated façade constructions. The participants rated both the loudness and the annoyance of 60 sounds. The playback levels were between 12 and 46 dB LAeq, covering the essential range of road-traffic noise usually measured inside residential dwellings. Linear correlations were determined between the SNQ values of the façades and the subjective ratings. Rw + C50-3150 explained the subjective ratings best when the five sound types were equally considered. It was also the most suitable SNQ for the standard road-traffic spectrum of ISO 717-1. The results of this study can be useful in the development of future standards.

Subjective and objective rating of spectrally different pseudorandom noises--implications for speech masking design.

Artificial sound masking is increasingly used in open-plan offices to improve speech privacy and to reduce distraction caused by speech sounds. Most of the masking sounds are based on pseudorandom continuous noise filtered to a specific spectrum that should be optimized in respect with speech masking efficiency and comfort. The aim of this study was to increase basic understanding regarding the comfort. The second aim was to determine how well objective rating methods (15 different noise indices) predict the subjective ratings. Twenty-three subjects rated the loudness, disturbance, pleasantness, and six other subjective measures of 11 spectrally different noises in laboratory conditions. Speech was not present during the experiment. All sounds were presented at 42 dB LAeq within 50-10,000 Hz. Unexpectedly, the subjects were most satisfied with sounds having emphasis on low frequencies. A sound having a slope of -7 dB per octave increment resulted in the highest satisfaction. Changes in subjective ratings were reasonably well predicted by five noise indices, while many well-known noise indices frequently used in building design underperformed in this task. The results are expected to benefit in the design of masking sounds and other appliances.