Designing sound and visual components for enhancement of urban soundscapes.

The aim of this study is to investigate the effect of audio-visual components on environmental quality to improve soundscape. Natural sounds with road traffic noise and visual components in urban streets were evaluated through laboratory experiments. Waterfall and stream water sounds, as well as bird sounds, were selected to enhance the soundscape. Sixteen photomontages of a streetscape were constructed in combination with two types of water features and three types of vegetation which were chosen as positive visual components. The experiments consisted of audio-only, visual-only, and audio-visual conditions. The preferences and environmental qualities of the stimuli were evaluated by a numerical scale and 12 pairs of adjectives, respectively. The results showed that bird sounds were the most preferred among the natural sounds, while the sound of falling water was found to degrade the soundscape quality when the road traffic noise level was high. The visual effects of vegetation on aesthetic preference were significant, but those of water features relatively small. It was revealed that the perceptual dimensions of the environment were different from the noise levels. Particularly, the acoustic comfort factor related to soundscape quality considerably influenced preference for the overall environment at a higher level of road traffic noise.