Subjective evaluation on the effect of tonal components contained in environmental noises

Recently in Japan, noises from wind turbines and domestic use heat source sometimes cause increase of noise annoyance due to low-frequency tonal components. The purpose of this study is to investigate the effects of the tonal components to the noisiness of the environmental noise. The authors conducted auditory test to evaluate the noisiness of noise, using 7-step rating scale method. The stimuli were composed of a broad-band noise and a low frequency tonal component. The A-weighted sound pressure levels of broadband noise modelling the environmental noise outdoor and indoor were 25, 30, 35 dBs. As the tonal component added to the broadband noise, frequency and tonal audibility were varied as 40, 50, 100, 200, 400 Hz, and 0, 3, 6, 9, 12 dBs, respectively. The effect of the tonal components on noisiness were determined as tonal adjustment by comparing the noisiness of tonal noise to that of noises without tonal components. The values of the tonal adjustment were within 0 to 7 dBs. Comparing the presentation level, the value of the tonal adjustment was larger in lower presentation level.