The role of the microphone in parametrizing the acoustics of three rectangular concert spaces

Abstract

The scientific method is a principle that states that no theory or model of nature is tenable, unless the results it predicts are in accord with experiment. The concert hall, as a physical system, has long been misunderstood in terms of the effects it has on acoustics. This paper discusses the application of the scientific method to the measurement of acoustical parameters in three renowned spaces: Boston Symphony Hall, the Troy Music Hall, and the Union College Memorial Chapel. The results of the experiments strongly suggest that no characterization of a hall's acoustics is possible without the specification of the microphone used in the measurement. Microphones ranging from a 1/2-in. omnidirectional transducer to an acoustic manikin employing a 1/2-in. omnidirectional transducer produce clearly identifiable differences in reverberation times and other widely used parameters that are calculated from the transient response of the space. These results suggest, contrary to the belief of many, that acoustical science applied to concert halls is not an exact science, but pathological in character. It is concluded that acoustical comparisons between different spaces are not possible unless the type of microphone, as well as its placement and orientation in the space, are specified. [Work supported in part by the Audio Engineering Society Education Foundation.]