Research suggests that visual impressions of natural compared with urban environments facilitate recovery after psychological stress. To test whether auditory stimulation has similar effects, 40 subjects were exposed to sounds from nature or noisy environments after a stressful mental arithmetic task. Skin conductance level (SCL) was used to index sympathetic activation, and high frequency heart rate variability (HF HRV) was used to index parasympathetic activation. Although HF HRV showed no effects, SCL recovery tended to be faster during natural sound than noisy environments. These results suggest that nature sounds facilitate recovery from sympathetic activation after a psychological stressor.

There is a need for a model that identifies underlying dimensions of soundscape perception, and which may guide measurement and improvement of soundscape quality. With the purpose to develop such a model, a listening experiment was conducted. One hundred listeners measured 50 excerpts of binaural recordings of urban outdoor soundscapes on 116 attribute scales. The average attribute scale values were subjected to principal components analysis, resulting in three components: Pleasantness, eventfulness, and familiarity, explaining 50, 18 and 6% of the total variance, respectively. The principal-component scores were correlated with physical soundscape properties, including categories of dominant sounds and acoustic variables. Soundscape excerpts dominated by technological sounds were found to be unpleasant, whereas soundscape excerpts dominated by natural sounds were pleasant, and soundscape excerpts dominated by human sounds were eventful. These relationships remained after controlling for the overall soundscape loudness (Zwicker’s N10), which shows that ‘informational’ properties are substantial contributors to the perception of soundscape. The proposed principal components model provides a framework for future soundscape research and practice. In particular, it suggests which basic dimensions are necessary to measure, how to measure them by a defined set of attribute scales, and how to promote high-quality soundscapes.

An association has been reported between long-term exposure to road traffic noise and the risk of myocardial infarction (MI), but the evidence is limited and inconclusive. No previous study has simultaneously analyzed the role of exposure to noise and air pollution from road traffic in the risk of MI. A population-based case-control study on MI was conducted 1992-1994 in Stockholm County. Participants answered a questionnaire and underwent a physical examination. Residential exposure to noise and air pollution from road traffic between 1970 and 1992-1994 was assessed for 3666 participants (1571 cases of MI and 2095 controls), based on residential history combined with information on traffic intensity and distance to nearby roads. Information was also obtained on factors potentially affecting the relationship between noise exposure and MI, such as noise annoyance. The correlation between long-term individual exposure to noise and air pollution from traffic was high (r = 0.6). The adjusted odds ratio for MI associated with long-term road traffic noise exposure of 50 dBA or higher was 1.12 (95% confidence interval = 0.95-1.33). In a subsample, defined by excluding persons with hearing loss or exposure to noise from other sources, the corresponding odds ratio was 1.38 (1.11-1.71), with a positive exposure-response trend. No strong effect modification was apparent by sex or cardiovascular risk factors, including air pollution from road traffic. The results lend some support to the hypothesis that long-term exposure to road traffic noise increases the risk for MI.

A field experiment was conducted to explore whether water sounds from a fountain had a positive impact on soundscape quality in a downtown park. In total, 405 visitors were recruited to answer a questionnaire on how they perceived the park, including its acoustic environment. Meanwhile the fountain was turned on or off, at irregular hours. Water sounds from the fountain were not directly associated with ratings of soundscape quality. Rather, the predictors of soundscape quality were the variables “Road-traffic noise” and “Other natural sounds”. The former had a negative and the latter a positive impact. However, water sounds may have had an indirect impact on soundscape quality by affecting the audibility of road-traffic and natural sounds. The present results, obtained in situ, agree with previous results in soundscape research that the sounds perceived—particularly roadtraffic and natural sounds—explain soundscape quality. They also agree with the results from laboratory studies that water sounds may mask road-traffic sounds, but that this is not simple and straight forward. Thus sound should be brought into the design scheme when introducing water features in urban open spaces, and their environmental impact must be thoroughly assessed empirically

Research suggests that blind people are superior to sighted in echolocation, but systematic psychoacoustic studies on environmental conditions such as distance to objects, signal duration, and reverberation are lacking. Therefore, two experiments were conducted. Noise bursts of 5, 50, or 500 ms were reproduced by a loudspeaker on an artificial manikin in an ordinary room and in an anechoic chamber. The manikin recorded the sounds binaurally in the presence and absence of a reflecting 1.5-mm thick aluminium disk, 0.5 m in diameter, placed in front, at distances of 0.5 to 5 m. These recordings were later presented to ten visually handicapped and ten sighted people, 30–62 years old, using a 2AFC paradigm with feedback. The task was to detect which of two sounds that contained the reflecting object. The blind performed better than the sighted participants. All performed well with the object at < 2 m distance. Detection increased with longer signal durations. Performance was slightly better in the ordinary room than in the anechoic chamber. A supplementary experiment on the two best blind persons showed that their superior performance at distances > 2 m was not by chance. Detection thresholds showed that blind participants could detect the object at longer distances in the conference room than in the anechoic chamber, when using the longer-duration sounds and also as compared to the sighted people. Audiometric tests suggest that equal hearing in both ears is important for echolocation. Possible echolocation mechanisms are discussed.