Annoyance Suppression Effect of Narrow-Band Color Noises and Water Sounds on Low-Frequency Tonal Noise

Due to the increasing noise pollution, noise control has drawn more and more public attention. Different from traditional methods to reduce noise energy such as active and passive noise control, suppressing noise annoyance through adding sounds is another choice. In previous studies, water sounds are usually used to adjust the annoyance of traffic noise, but the suppression effect of the water sounds varies from person to person. Low-frequency tonal noise is one kind of typical and common mechanical noise, i.e., substation noise, whose annoyance is caused by tonal perception and higher energy in low frequency is difficult to suppress even though adding sounds. In this study, different controllable sounds (water sounds and narrow-band color noises) with different masker-to-noise ratios (MNRs) were added to low-frequency tonal noise to investigate the annoyance suppression effect through listening tests. Furthermore, in order to evaluate the quantitative suppression effect, the standard sample method (SSM) was applied in the listening tests to convert the annoyance difference into the difference of equivalent sound pressure level of 1 kHz and 70 dB pure tone (ΔSPL_1kHz,70dB). Results show that different kinds of water sounds and narrow-band color noises effectively reduce noise annoyance. The optimal result comes from adding one kind of water sound, which reduces the annoyance of substation noise by 27.24%, equivalent to reducing ΔSPL_1kHz,70dB by 6.5 dB. Finally, the annoyance prediction model of combined noises is established to choose controllable sounds and predict the suppression effect of annoyance.