# Effect of Audio-Visual Factors in the Evaluation of Crowd Noise
## 1 Introduction
However, due to the limitations of geographical conditions, it is difficult to present the sound environment with different attributes during the same survey; furthermore, this method can downplay other factors in the natural environment, including olfactory and other sensory elements that can affect perception [32]. Hence, laboratory research involves more widespread use of methods reproducing the sound environment. Through a series of field investigations and laboratory experiments, [PERSON], [PERSON], [PERSON], and [PERSON] (1983) studied the influence of sound on preferences for outdoor environments and found an interaction between sound and vision. They also compared the differences between field research and laboratory research. Laboratory research has since evolved into a developed research method for audio-visual research [33]. To study audio-visual interactions in the laboratory, researchers now mainly focus on the subjective evaluation of factors that influence the perception of the environment. In a noisy environment, people unconsciously raise their voices [34; 35]. Crowd density is an environmental factor expressed as the number of people in a space divided by the area of the space. Crowd density estimates were first used for crowd monitoring to determine when an area reaches a greater-than-expected crowd density that could endanger the safety of people [36]. Subsequently, crowd density has been used in various research areas, such as environmental pollution, building technology, and landscape design. Previous studies have shown that crowd density affects certain spatial or environmental characteristics in a given space [37]. In addition, previous studies have shown that crowd density affects behavior [38]. Regarding the masking effect of human sounds, [PERSON], [PERSON], and [PERSON] pointed out that human sounds placed near temporary open-air markets with adjacent road traffic can effectively mask traffic noise [39]. [PERSON] et al. also pointed out that urban noises, such as traffic noise, construction noise, and community noise, can be effectively masked by human sounds [40]. However, studies on crowd distribution and the impact of human sound on the sound environment of urban public spaces are limited. Crowds can be regarded as sound sources and absorbers. The effect of crowd density on the sound environment is studied through subjective features such as audio-visual interaction evaluations [41]. Therefore, this study aimed to research the following three questions: (1) What is the effect of human sounds at different volumes on the overall sound environment when superimposed on other sounds? (2) What is the effect of crowd density on overall evaluations of the current environment, both visual and auditory? (3) With the same human sound as the background, do changes in the visual scene affect people's evaluation of the sound environment? This study examines the audio-visual impact of human sound on evaluations of the soundscapes of urban public spaces through experiments on the audio-visual interaction of four main groups of sound sources and visual images in urban public spaces.