A laboratory investigation into the effect of quiet-time interval between aircraft noise events on overall noisiness.

In order to investigate the effect of the quiet-time interval between aircraft noise events on the overall negative impression of aircraft noise, psychological experiments were conducted in which the quiet-time interval was varied and the number of events and duration of each stimulus were taken into account. For equal A-weighted equivalent continuous sound pressure level (LAeq) among the stimuli, it was found that overall noisiness decreased as the quiet-time interval ratio of the stimulus was increased. It was also found that the correlation between overall noisiness and LAeq was improved by adjusting for the quiet-time interval ratio or the number of events included in the stimuli, especially when participants paid attention to changes in the instantaneous noise level. This study reveals that LAeq is a good basis for evaluating the negative impressions of aircraft noise, but that correcting for the quiet-time interval and/or number of flights improves the correlation between LAeq and the negative impression in such aircraft noise situations.

Overall judgment of loudness of time-varying sounds.

Listeners can judge the overall loudness of time-varying sounds quite easily, i.e., assign a single value that represents the loudness of the entire sound. This holds even if the duration is long and the judgment includes memory effects. Different metrics for calculating overall loudness have been developed. They agree that overall loudness is higher than the mean of loudness over time. Percentiles like the N5, the loudness being exceeded 5% of the time, are adopted by ISO 532-1. In the present study the concept of an energy mean known from level measurements (ISO 1996-1) was applied to the loudness domain. This equivalent continuous loudness level, LLP, was compared to the N5 using a set of real-world sounds that was orthogonal between the two metrics over a wide dynamic range of 30 phon. Cross-modality matching with line length was used in three experiments with a focus on either the overall judgment of loudness, continuous judgment while a sound was played, or both. The LLP showed considerably higher correlations with overall judgments than N5. Comparing continuous instantaneous judgment with calculated instantaneous loudness suggests that the participants might have focused on the sounds' prominent portions.

Statistical Analysis for Subjective and Objective Evaluations of Dental Drill Sounds.

The sound produced by a dental air turbine handpiece (dental drill) can markedly influence the sound environment in a dental clinic. Indeed, many patients report that the sound of a dental drill elicits an unpleasant feeling. Although several manufacturers have attempted to reduce the sound pressure levels produced by dental drills during idling based on ISO 14457, the sound emitted by such drills under active drilling conditions may negatively influence the dental clinic sound environment. The physical metrics related to the unpleasant impressions associated with dental drill sounds have not been determined. In the present study, psychological measurements of dental drill sounds were conducted with the aim of facilitating improvement of the sound environment at dental clinics. Specifically, we examined the impressions elicited by the sounds of 12 types of dental drills in idling and drilling conditions using a semantic differential. The analysis revealed that the impressions of dental drill sounds varied considerably between idling and drilling conditions and among the examined drills. This finding suggests that measuring the sound of a dental drill in idling conditions alone may be insufficient for evaluating the effects of the sound. We related the results of the psychological evaluations to those of measurements of the physical metrics of equivalent continuous A-weighted sound pressure levels (LAeq) and sharpness. Factor analysis indicated that impressions of the dental drill sounds consisted of two factors: "metallic and unpleasant" and "powerful". LAeq had a strong relationship with "powerful impression", calculated sharpness was positively related to "metallic impression", and "unpleasant impression" was predicted by the combination of both LAeq and calculated sharpness. The present analyses indicate that, in addition to a reduction in sound pressure level, refining the frequency components of dental drill sounds is important for creating a comfortable sound environment in dental clinics.

Exposure-response relationship of wind turbine noise with self-reported symptoms of sleep and health problems: A nationwide socioacoustic survey in Japan.

The association of wind turbine noise (WTN) with sleep and physical/mental health has not been fully investigated. To investigate the relationship of WTN with the prevalence of self-reported symptoms of sleep and health problems, a socioacoustic survey of 1079 adult residents was conducted throughout Japan (2010-2012): 747 in 34 areas surrounding wind turbine plants and 332 in 16 control areas. During face-to-face interviews, the respondents were not informed of the purpose of the survey. Questions on symptoms such as sleeplessness and physical/mental complaints were asked without specifying reasons. Insomnia was defined as having one or any combination of the following that occurs three or more times a week and bothers a respondent: Difficulty initiating sleep, difficulty maintaining sleep, premature morning awakening, and feeling of light overnight sleep. Poor health was defined as having high scores for health complaints, as determined using the Total Health Index, exceeding the criteria proposed by the authors of the index. The noise descriptor for WTN was LAeq,n outdoor, estimated from the results of actual measurement at some locations in each site. Multiple logistic analysis was applied to the LAeq,n and insomnia or poor health. The odds ratio (OR) of insomnia was significantly higher when the noise exposure level exceeded 40 dB, whereas the self-reported sensitivity to noise and visual annoyance with wind turbines were also independently associated with insomnia. OR of poor health was not significant for noise exposure, but significant for noise sensitivity and visual annoyance. The above two moderators appear to indicate the features of respondents who are sensitive to stimuli or changes in their homeostasis.