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)).
Vos
Joos
J
TNO Human Factors, P.O. Box 23, 3769 ZG Soesterberg, The Netherlands.