title: Optimum speech level to minimize listening difficulty in public spaces.
abstract: For ideal speech communication in public spaces, it is important to determine the optimum speech level for various background noise levels. However, speech intelligibility scores, which is conventionally used as the subjective listening test to measure the quality of speech communication, is near perfect in most everyday situations. For this reason, it is proposed to determine optimum speech levels for speech communication in public spaces by using listening difficulty ratings. Two kinds of listening test were carried out in this work. The results of the tests and our previous work [M. Morimoto, H. Sato, and M. Kobayashi, J. Acoust. Soc. Am. 116, 1607-1613 (2004)] are jointly discussed for suggesting the relation between the optimum speech level and background noise level. The results demonstrate that: (1) optimum speech level is constant when background noise level is lower than 40 dBA, (2) optimum speech level appears to be the level, which maintains around 15 dBA of SN ratio when the background noise level is more than 40 dBA, and (3) listening difficulty increases as speech level increases under the condition where SN ratio is good enough to keep intelligibility near perfect.
authors.affiliation: Environmental Acoustics Laboratory, Faculty of Engineering, Kobe University, Rokko, Nada, Kobe 657-8501 Japan. masaaki.kobayashi@toda.co.jp
authors.forename: Masaaki
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Morimoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sato
authors.forename: Hayato
authors.initials: H
authors.lastname: Sato
mesh_terms: D000328:Adult; D003144:Communication Barriers; D004777:Environment; D005260:Female; D006801:Humans; D008144:Loudness Perception; D008297:Male; D009622:Noise; D013065:Speech Intelligibility; D013067:Speech Perception