ANNOYANCE CAUSED BY SOUNDS OF WHEELED AND TRACKED VEHICLES

In a laboratory experiment, the relationship between the annoyance cau sed by sounds of tracked and wheeled vehicles was investigated. Sounds of various vehicles, ranging from a main battle tank (MET) to a passe nger car, were recorded at several distances. Subjects were presented with these sounds and were asked to judge the annoyance if they were e xposed to them at home on a regular basis. Overall, sounds emanated fr om military tracked vehicles were judged to be less annoying than civi l passenger cars, provided that the indoor A-weighted sound-exposure l evels (ASELs) were the same. It should be noted that receiver distance and operating conditions were not specifically matched for military a nd civil vehicles but were chosen to represent typical ranges of value s found in practice. For steady-speed conditions, the sounds were judg ed to be equally annoying if the (indoor) ASELs of the tracked armored personnel carrier (APC) and the MBT exceeded that of a passenger car by 5 and 10 dB, respectively. In specific driving conditions such as a lternate accelerations and decelerations, however, these differences w ere smaller. For ASELs below 55 dB, passenger cars were found to be mo re annoying than heavier wheeled vehicles, such as a bus or a truck wi th a trailer. The data indicate that the difference between the high-f requency part and the low-frequency part of the spectrum might play a role in the annoyance. With respect to noise-zoning procedures it is h ighly interesting that the outdoor ASEL could predict the annoyance, a s rated indoors, better than could any indoor noise measure. The 5- an d 10-dB bonuses to the indoor level of the APC and the MET, respective ly, were reduced to 1 and 3 dB if the dose was measured outdoors. (C) 1997 Acoustical Society of America.