BACH, a new binaural room acoustical measure

Abstract

This study reports on acoustical field measurements made in a major survey of 41 Catholic churches in Portugal built in the last fourteen centuries. Binaural measurements were taken in each church using a dual-channel real-time frequency analyzer to calculate the coherence values between the signals at both ears in 1/3-octave frequency bands. From the coherence values a new binaural acoustical measure was developed and called BACH (BinauralAcousticalCoHerence). Monaural acoustical measurements were also taken at several source/receiver locations using the impulse response method. BACH was shown to be an orthogonal parameter in statistical tests with nine other monaural acoustical measures (RT, EDT, C80, D, TS, L, BR—RT, BR—L, and RASTI) and fifteen architectural parameters. Information was collected regarding the quality of music in each church. ANOVA tests were performed to examine the significance of the differences among the groups of equal subjective quality ratings. The author wanted to test the hypothesis that this new binaural acoustical measure can be useful in estimating the general subjective quality of churches regarding music. A linear correlation coefficient near 0.7 was found between the BACH and the subjective quality ratings that supported the stated hypothesis. This is exploratory research and developments are being tested to improve the model. [Work supported by JNICT/Ministry of Planning and Univ. of Porto, Portugal.]