HYBRID METHOD TO CHARACTERIZE SOUND-FIELD DIFFUSENESS OF MULTIPURPOSE UNIVERSITY AUDITORIUMS USING SUBJECTIVE AND OBJECTIVE EVALUATION

摘要

There exist spaces with activities encompass the need to eliminate excessive reverberation while maintaining a certain amount of sound energy such as university auditoriums. The challenge is to create a similar listening quality at the audience seats of good speech intelligibility, without sound amplification. This leads to the current trend of using diffusive surfaces as the room acoustics solution. Several methods have been proposed to quantify the sound field diffuseness but none has combined with the subjective assessment. This paper demonstrates a method that combines subjective and objective evaluation using selected parameters. Analysis of the early and late reflections of the room impulse responses (RIR) was done. The RIRs were obtained from field measurement and computer simulation using CATT-Acoustic software of selected rooms. The method enables to observe the ability of diffusive surfaces in reducing comb-filtering effect of early reflections, which is when speech is heard as mumbled. There will be less comb-like signals in the frequency response. The speech intelligibility and the acoustical quality is evaluated using T_(30), EDT, C_(50), C_(80) and background noise level. Noticeable differences of the auditory experience were investigated by utilizing computer-based survey techniques, given the current software auralization capabilities. The results based on statistical analysis demonstrate the users' ability to distinguish the intensity, clarity, and reverberation created within the rooms, with and without the diffusive surfaces. This approach provides further application in synthesizing auditory events within the multipurpose auditorium.