A survey on acoustic comfort of conversing in multi-group conversation spaces

Restaurants or cafes can be categorized as "Multi-group conversation space (MGCS)" where more than one group are conversing within the group. Speech intelligibility and speech privacy are considered to be two major factors for comfortable speech communication and, in particular, MGCS requires optimum conditions for both of the factors because, for example, conversation would be uncomfortable when a café was too quiet and little reverberant as the conversation of multi groups could be clearly heard each other and, instead, when it was too noisy the conversation would be disturbed. Acoustic factors of background noise level and reverberation affect speech intelligibility and privacy but only a few studies have been conducted to investigate the optimum conditions. The purpose of this study is to find people's evaluation on the easiness of conversation and how the evaluation is affected by acoustic and special properties in actual MGCSs, and an acoustic measurement and a questionnaire was conducted at three cafes. Room impulse responses were measured and acoustic parameters such as reverberation time and D50 were calculated from them. Also and noise levels were measured during the operating time. The questionnaire consisted of six questions of easiness of conversing, comfortableness, noisiness, concern with the surrounding conversation, feeling of reverberation and intelligibility of speech within the group with five-step evaluation scale.As a result, the evaluation on intelligibility of speech within the group was lower in a café where the level of the background music was higher than those in the other cafes but, at the same time, the mean value of evaluation on easiness of conversing was similar while both of the ratio of positive and negative evaluations were greater than those in the others. Among the acoustic parameters, D50 had the greatest correlation coefficient with the evaluation of easiness of conversing.