MOTOR VEHICLE EXTERIOR SOUND QUALITY IMPROVEMENT FOR INDOORS

摘要

The objectives of this study are these three items. 1) To find better indices than dB(A) for representing annoyances caused by motor vehicle traffic noise along highways. 2) To find the frequency range of motor vehicle exterior noise that should primarily be controlled to achieve better indoor sound environment along highways. 3) To find suitable vehicle driving conditions for evaluating indoor sound environment. To obtain the desired results psycho-acoustic experiments were conducted. Firstly, sound samples were collected with microphones placed at such locations as on a sidewalk, in front of a small house and at the center of a room inside of the house. The number of test vehicles was fifteen, consisting of six motorcycles and nine passenger cars. The driving conditions were full acceleration and mild acceleration usually found in normal traffic flow. Secondly, semantic differentiation method was used. Ten pairs of adjectives were used to scale the impressions of each sound sample. Finally, physical characters of the sound samples and their subjective evaluations were compared.