Annoyance caused by the low-frequency sound produced by aircraft during takeoff.

In a laboratory study, the indoor annoyance caused by the sound produced by aircraft during the takeoff on the runway is investigated. This aircraft sound is dominated by relatively high sound levels in the 16 and 31.5 Hz octave bands. Road-traffic and passenger railway sounds, which lack high sound levels in these octave bands, are included as references. The sounds are presented at indoor A-weighted equivalent levels of 32 and 42 dB. The participants are males and females between 20 and 40, or between 40 and 60 years of age. The indoor annoyance increased with sound level, but it was not affected by source type. Moreover, it was not or hardly affected by gender or age. With the dose expressed as A-weighted outdoor levels, the penalty for the aircraft sound and the bonus for the passenger railway sound at least qualitatively correspond to those obtained in pertinent previous studies. In the present study, such adjustments can be avoided by including the difference between the outdoor C-weighted and A-weighted levels as a second predictor, yielding an explained variance in the mean indoor annoyance ratings as high as 98%.

Comments on "Influences of low-frequency energy and testing environment on annoyance responses to supersonic aircraft noise when heard indoors" [J. Acoust. Soc. Am. 148(1), 414-429 (2020)].

Carr, Davies, Loubeau, Rathsam, and Klos [J. Acoust. Soc. Am. 148, 414-429 (2020)] found that indoor annoyance caused by sonic booms may be predicted from the A-weighted sound exposure level and the heaviness of the booms. Moreover, they suggest that, irrespective of the outdoor-to-indoor sound reduction, indoor annoyance may be predicted from outdoor sound levels. The present paper shows that their data to some extent also support a model in which the contribution of heaviness is level-dependent and that data reported in the literature point out that it is unlikely that indoor annoyance is independent of the degree of façade attenuation.

Estimating parameter values in a model for rating shooting sounds from field survey data.

Laboratory studies show that the annoyance caused by shooting sounds can be predicted from the outdoor A- and C-weighted sound exposure levels (ASELs and CSELs; LAE and LCE). For any single event, the rating sound level, Lr,s in decibel, is given by Lr,s = LAE + 12 + ß(LCE - LAE)(LAE - α). On the basis of the laboratory results α = 47 dB and ß = 0.015 dB-1 were recommended. In the present study, parameter values α and ß are re-estimated. Subjective reactions to shooting and road-traffic sounds were determined for 400 respondents divided among 15 residential areas. Also, the noise dose for road traffic was calculated and the ammunition spent in the 12 months preceding the administration of the questionnaire was listed. Next, for all impulsive sources, the required ASELs and CSELs received in the residential areas were calculated. Based on the data from the majority of the residential areas, the estimated ß in combination with α = 45 dB is equal to 0.025 dB-1. At the lower and upper limits of the 95% confidence interval of ß, as obtained with the help of a bootstrap method, ß is equal to 0.013 and 0.037 dB-1, respectively.

Enhanced awakening probability of repetitive impulse sounds.

In the present study relations between the level of impulse sounds and the observed proportion of behaviorally confirmed awakening reactions were determined. The sounds (shooting sounds, bangs produced by door slamming or by container transshipment, aircraft landings) were presented by means of loudspeakers in the bedrooms of 50 volunteers. The fragments for the impulse sounds consisted of single or multiple events. The sounds were presented during a 6-h period that started 75 min after the subjects wanted to sleep. In order to take account of habituation, each subject participated during 18 nights. At equal indoor A-weighted sound exposure levels, the proportion of awakening for the single impulse sounds was equal to that for the aircraft sounds. The proportion of awakening induced by the multiple impulse sounds, however, was significantly higher. For obtaining the same rate of awakening, the sound level of each of the successive impulses in a fragment had to be about 15-25 dB lower than the level of one single impulse. This level difference was largely independent of the degree of habituation. Various explanations for the enhanced awakening probability are discussed.

Annoyance caused by the sounds of a magnetic levitation train.

In a laboratory study, the annoyance caused by the passby sounds from a magnetic levitation (maglev) train was investigated. The listeners were presented with various sound fragments. The task of the listeners was to respond after each presentation to the question: "How annoying would you find the sound in the preceding period if you were exposed to it at home on a regular basis?" The independent variables were (a) the driving speed of the maglev train (varying from 100 to 400 km/h), (b) the outdoor A-weighted sound exposure level (ASEL) of the passbys (varying from 65 to 90 dB), and (c) the simulated outdoor-to-indoor reduction in sound level (windows open or windows closed). As references to the passby sounds from the maglev train (type Transrapid 08), sounds from road traffic (passenger cars and trucks) and more conventional railway (intercity trains) were included for rating also. Four important results were obtained. Provided that the outdoor ASELs were the same, (1) the annoyance was independent of the driving speed of the maglev train, (2) the annoyance caused by the maglev train was considerably higher than that caused by the intercity train, (3) the annoyance caused by the maglev train was hardly different from that caused by road traffic, and (4) the results (1)-(3) held true both for open or closed windows. On the basis of the present results, it might be expected that the sounds are equally annoying if the ASELs of the maglev-train passbys are at least 5 dB lower than those of the intercity train passbys. Consequently, the results of the present experiment do not support application of a railway bonus to the maglev-train sounds.

A- and C-weighted sound levels as predictors of the annoyance caused by shooting sounds, for various façade attenuation types.

In a previous study on the annoyance caused by a great variety of shooting sounds [J. Acoust. Soc. Am. 109, 244-253 (2001)], it was shown that the annoyance, as rated indoors with the windows closed, could be adequately predicted from the outdoor A-weighted and C-weighted sound-exposure levels [ASEL (L(AE)) and CSEL (L(CE))] of the impulse sounds. The explained variance in the mean ratings by (outdoor) ASEL was significantly increased by adding the product (L(CE) - L(AE))(L(AE)) as a second variable. In the present study it was investigated to which extent the additional contribution of the second predictor is also relevant for façade attenuation types with lower and higher degrees of sound isolation than applied previously. Twenty subjects rated the indoor annoyance caused by 11 different impulse types produced by firearms ranging in caliber from 7.62 to 155 mm, at various levels and for five façade attenuation conditions. The effect of façade attenuation on the ratings was large and consistent. In all conditions, an optimal prediction of the annoyance was obtained with outdoor ASEL as the first, and (L(CE) - L(AE))(L(AE)) as the second predictor. The benefit of the second predictor, expressed as the increase in the explained variance, ranged from 2.5 to 55 percent points, and strongly increased with the degree of façade attenuation. It was concluded that for the determination of the rating sound level, the acoustic parameters ASEL and CSEL are very powerful. In addition, the results showed that for the whole set of impulses included, the annoyance could also be predicted very well by the weighted sum of indoor ASEL and the product (L(CE) - L(AE))(L(AE)).