Experimental studies on speech level and room acoustic condition focusing on speech privacy

Abstract

Recently, concerns about speech privacy to avoid oral information leakage at medical facilities are increasing continuously in Japan. In order to achieve the requirements of the speech privacy, standardization has also been discussed. On discussing the speech privacy, speech level is one of the most important factors. This study investigated the speech levels of Japanese talkers and the relationships between the speech levels and the room acoustic conditions (reverberation time, ratio of direct and reflected sound, and loudness of background noise). Subjective experiments were conducted under three conversation conditions; normal voice level with a partner sitting 1 m away, raised voice level with the partner sitting 3 m away, and voice level considering overhearing about the contents by a third party. Acoustic environments were reproduced in an anechoic room with a binaural sound field simulation system. As a result, the speech levels of the three conversation conditions were varied. In the simulated test conditions, it was revealed that the room acoustic conditions affected on the speech levels, but the changes of the levels were small.