Influence of time variance on room impulse response measurement

Abstract

The measurement of room impulse response is made under the assumption that the sound propagation system is time invariant. Actually, however, the air in a room is usually moving and the temperature is changing to a greater or lesser extent. In order to examine the influence of such time variance on the measurement of room impulse response, experimental investigations were performed in a reverberation room in which the air was excited by fans and in a concert hall in which the air-conditioning system was operated. Impulse response measurements were performed by the maximum-length sequence (MLS) method and the sweep pulse (SP) method and these results were compared. From the results, it has been found that the reverberation decay tends to become steeper by repeating the impulse response measurement to get high signal-to-noise ratio and the SP method is more robust than the MLS method against the influence of time variance of the atmospheric condition in a room.