Yoshito Hidaka

Reverberation time directly obtained from a squared impulse response envelope

For the measurement of reverberation time, a method of directly regressing the envelope of a squared impulse response (direct method) was examined using 100 data obtained in 14 auditoria. The results were compared with those obtained by the integrated impulse response method (Schroeder method) and a very high coincidence was found between them. It has also found that the direct method is more robust to background noise than the Schroeder method and in the former method relatively short‐time data will do compared with the latter method.

Measurement of impulse response and its applications in room acoustics

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 d...

Comparison between the 1/10‐scale model experiment and the full‐scale measurement in a concert hall

In order to examine the accuracy of acoustic scale modeling, the experimental results of a 1/10‐scale model study performed for acoustical design of a concert hall and those measured in the full‐scale hall after the construction are compared. In the scale model study, the impulse responses were measured by the direct method using a spark discharge source and monaural and binaural microphone systems. For the measurement of the binaural impulse response, a 1/10‐scale dummy head system was made on a trial basis. In the real hall, impulse responses were measured by the sweep‐pulse method using a dodecahedral omnidirectional loudspeaker and monaural and binaural microphone systems. The monaural impulse responses were measured at the corresponding points in the scale model and the real hall, and such quantities as D50, C80, and Ts were obtained and compared. The binaural impulse responses measured in the model and real hall were convolved with the same sources of a variety of music and presented to the subjects...

Influence of time variance on room impulse response measurement

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.