Measurement of impulse response and its applications in room acoustics

Abstract

Impulse response includes almost all physical information of a linear system and it is also very important in room acoustics. Fortunately, owing to the recent development of digital signal processing techniques and instrumentation, it has become possible to make a precise and convenient measurement of impulse responses in rooms. In this paper, the practical techniques for this kind of measurement including scale model studies are introduced. For the measurement in real auditoriums, a sweep pulse is radiated many times from a dodecahedral omnidirectional loudspeaker and the responses are recorded on a DAT through an omnidirectional microphone or a dummy head system. From the recorded responses, impulse responses are obtained by synchronous averaging and deconvolution techniques. In scale model experiments, impulse responses are measured by using a spark discharge source and a scale model dummy head microphone. From the impulse responses measured in such ways, not only various room acoustic quantities are derived but also the sounds including the room response can be synthesized by making convolutions between the impulse responses and arbitrary dry source signals. This technique is effectively used for subjective evaluation of room acoustics. Some examples of the experimental results for real and scale model auditoriums will be demonstrated.