Effect of Audio-Visual Factors in the Evaluation of Crowd Noise

A crowd can be both a sound source and an absorber. The sound of human voices significantly impacts evaluations of acoustic indicators in urban public spaces. This study aimed to investigate whether human sound impacts evaluations of the overall environment from both visual and auditory aspects. Primary sound sources and scenes in Harbin, China urban public space served as the research object. Four sets of sound sources and six sets of images were collected in situ in urban public spaces. A subjective evaluation of both visual and auditory aspects was then performed in the laboratory. The results showed that when different types of sounds in urban public spaces are superimposed with human sound, the volume of human sound (45.6 dBA, 55.6 dBA, and 65.6 dBA) significantly affects the acoustic evaluation of the environment. When the superimposed sounds were birds and music, the evaluation of the environment decreased with the human voice increasing in volume. Crowd density and the surrounding visual environment also influence evaluations of the overall sound environment. In this study, the sound preference and acoustic comfort of birdsong and music decreased as the human sound volume increased. The effect of human sound combined with traffic sounds significantly decreased the scores for sound preference and acoustic comfort at higher volumes. The results of the experiments on audio-visual interactions in which people evaluated visual scenes showed that the influence of the visual density of a crowd on assessments of the sound environment is negatively related to the magnitude of the sound of the crowd. When human voices are at 45.6 dBA and 65.6dBA, there is a significant effect on the evaluation of visual scenes for high-density people. When the sound pressure level of human voices is the same, changes in the visual environment are more likely to affect people's evaluation of the overall sound environment.