Appropriate levels of natural sounds to enhance soundscapes in urban areas

Soundscape in an urban environment can be improved by introducing pleasant natural sounds. In order to achieve optimal soundscape masking effect, it is necessary to investigate the appropriate levels of natural sounds against target noise level. This study aims to investigate optimal sound levels of natural sounds to mask traffic noises and to increase overall preference of sound environment. Various natural sounds (bird, insect, and water sounds) were selected as a positive masker for road traffic noise. Visual environments were also recorded by using a 360° camera. Virtual reality techniques for reproduction of audio-visual environments were employed to evaluate soundscape under laboratory conditions. The laboratory experiments were performed to determine the ranges of signal-to-noise ratio between natural sounds and traffic noise to achieve lower perceived loudness of traffic noise and higher soundscape quality. Acoustic parameters for the stimuli were calculated to quantify the masking effects.