Investigation on Influence of Additional Sound on Comfortableness of Living Environment

Abstract

Adding a sound to a certain environment is likely to be effective for design of impression there in acoustical point of view. However, until now, little is known about the effectiveness of additional sound on the change in impression. In order to investigate the effect of additional sound, an experiment was conducted by using three kinds of audio-visual materials offering three environments and five kinds of additional sounds. The audio-visual materials were respectively recorded at ``forest,'' ``park,'' and ``shopping street.'' They represent ``natural,'' ``artificial green,'' and ``urban'' environments, respectively. Five kinds of sound stimuli were respectively chosen as: ``bird singing,'' ``sound of stream,'' ``roaring of waves,'' ``traffic noise,'' and ``hum of voices.'' The former three stimuli are regarded as sounds in nature, while the latter two are regarded as artificial ones. The experiment was based on the method of paired comparison, consisting of the unprocessed original audio-visual material and that with one of the additional sounds. The subjects evaluated relative comfortableness and naturalness of each pair. Sound pressure level of the additional sound was controlled in order to discuss the influence of the loudness of the additional sound to the evaluation. The experimental results showed that the comfortableness was improved when the additional sound was `bird singing' or `sound of stream' categorized in the nature sound and its sound pressure level was a little lower than that at the original environment. Moreover, it was found out that the naturalness is degraded gradually for almost of the additional sound stimuli, as their sound pressure level is increased.