[Influence of environmental noise on sleep quality and sleeping disorders-implications for health]

The Evaluation of Conventional, Electric and Hybrid Electric Passenger Car Pass-By Noise Annoyance Using Psychoacoustical Properties

Road traffic noise is one of the most prominent sources of urban noise pollution. Recently, as a result of the electrification of vehicles, lower noise levels are expected in urban areas at speeds below 50 km/h. The commonly used physical descriptor, the A-weighted sound pressure level, does not sufficiently characterize the perceived annoyance of either combustion engine or electric passenger car pass-by noises. Psychoacoustical descriptors are advantageous for characterization purposes. The objective of this study was to evaluate the perceived annoyance caused by the noise from internal combustion engine, electric, and hybrid passenger cars using psychoacoustical properties. To achieve this objective, the following steps were conducted. First, the binaurally recorded sounds of 40 cars from different brands with different motorization were presented to the subjects who indicated the intensity of their perceived annoyance on a quasi-continuous scale. Second, the signal and psychoacoustical properties of the recorded sounds were analyzed. Third, a new annoyance index was developed, based on annoyance judgments and signal and psychoacoustical properties, to characterize the annoyance caused by pass-by noises. One of the novel aspects of this study is the consideration of not only the pass-by sounds of the internal combustion engine passenger cars, but also the pass-by sounds of hybrid and electric passenger cars. An acceleration from idle to a target speed of 50 km/h was selected as a traffic pass-by situation, which differs from those considered in previous studies. The results of the study show that psychoacoustical properties, such as loudness, tonality, roughness, and fluctuation strength, are very useful to characterize the annoyance perception, which is caused by single passenger car pass-by sounds in the above mentioned traffic situation. The developed index, which is a weighted combination of chosen psychoacoustical properties, can be very useful for traffic planning and traffic noise prevention measures.

The effect of room acoustics on the sleep quality of healthy sleepers

INTRODUCTION

Noise is one of the factors that can seriously disturb sleep, and sound volume is an important factor in this context. One strategy involves avoiding exposure to sounds in the night, while entail the minimization of background noise in a bedroom. The goal of this study was to investigate the effect of systematic sound attenuation on nocturnal sleep by influencing sound volume and reverberation within the context of room acoustics.

MATERIALS AND METHODS

On this basis, we designed a randomized, controlled crossover trial investigating 24 healthy sleepers (15 men and 9 women, aged 24.9 ± 4.1 years) with a body mass index (BMI) of 21.9 ± 1.6 kg/m2. Each participant slept for three consecutive nights at three different locations: (a) at our sleep lab, (b) at the participant's home, and (c) at an acoustically isolated room. In addition to conduct of polysomnography (PSG), subjective sleep quality and nocturnal noise level were measured at each location. We likewise measured room temperature and relative humidity.

RESULTS

Under conditions of equal sleep efficiency, a significant increase in deep sleep, by 16-34 min, was determined in an acoustically isolated room in comparison to the two other sleep locations. Fewer arousal events and an increase in rapid eye movement (REM) latency became evident in an acoustically isolated environment. Sleep in a domestic environment was subjectively better than sleep under the two test conditions.

DISCUSSION

For healthy sleepers, room acoustics influence the microstructure of sleep, without subjective morning benefit. Reduction of noise level and of reverberation leads to an increase in the amount of deep sleep and to reduction of nocturnal arousal events, which is especially important for poor sleepers.