On the effect of an acoustic diffuser in comparison with an absorber on the subjectively perceived quality of speech in a meeting room.

 Sanavi A., Schäffer B., Heutschi K. & Eggenschwiler K. , Laboratory for Acoustics / Noise Control, Empa Materials Science and Technology, CH-8600 Duebendorf, Switzerland

Acta Acustica United with Acustica, 103(6), 1037-1049 (2018).

Acoustic diffusers and absorbers are important components in room acoustic design and treatments to control unwanted reflections or to increase sound diffuseness, both of which may enhance subjectively perceived sound quality. To date, little is known about whether the treatment with diffusers or absorbers is more favorable for the subjectively perceived qualities, e.g. of speech, in ordinary rooms. The aim of this study was therefore twofold. The first aim was to investigate the effect of an acoustic diffuser on the subjectively perceived quality of speech in a meeting room. The second aim was to determine if and to what extent there are perceptual differences if the diffuser is replaced by an acoustic absorber. Two separate listening tests were performed with stimuli obtained from the convolution of measured binaural impulse responses of a meeting room with excellent speech intelligibility and speech samples recorded in an anechoic chamber. The results of the listening tests confirm that despite the already excellent speech intelligibility and low values of early decay time, speech quality can be further improved by introducing diffusers or acoustic absorbers, with absorbers improving the subjectively perceived speech quality slightly more than the diffusers.

Kurt Eggenschwiler
EMPA Abteilung Akustik
Überlandstrasse 129
CH-8600 Dübendorf
Tel. +41 44 823 41 77
Fax. +41 44 823 47 93
E-Mail: kurt.eggenschwiler@empa.ch