Effects of frequency characteristics of sound insulation on timbre of road traffic noise

摘要

An experiment was conducted concerning the effect of frequency characteristics of sound insulation on the impression of road traffic noise. Using semantic differential subjects judged the impression of stimuli which were simulated as if they were transmitted through facades having various sound transmission characteristics. The following results were found : (1) The timbre of road traffic noise was judged to be more powerful, fluctuating and unpleasant as the level of L{sub}AeQ became higher. But the impression of "shrill" was not influenced by the values of L{sub}AeQ When overall values of L{sub}AEQ were equal, the impression of "shrill" became stronger for the direct sounds than transmitted sounds. On the other hand, the calm impression became stronger for the sound equalized -5dB/oct. than direct sounds. The frequency characteristics of sound insulation affects the shrill impression. (2) The three factors were extracted by the factor analysis : they were "powerful" or "fluctuating," "metallic" and "unpleasant" factors. (3) The timbre of road traffic noise was judged to be more unpleasant as the level of L{sub}AEQ, loudness level based on ISO532B )LL{sub}z) and each octave band from 2kHz to 4kHz became higher. Also the effects of closing windows (difference between 63dBA (direct sounds) to 43dBA (equalized sounds)) suggested that the level of each octave band level over 2 kHz were related to the unpleasent impression. (4) It was suggested that the impression "unpleasant" could be approximately evaluated by the arithmetic average of sound pressure levels in octave bands from 500Hz to 4 kHz (SIL).