Study on the Measurements of Architectural Acoustie by Cross-Correlation Methods

상호상관법에 의한 건축음향측정에 관한 연구

A method of measuring impulse response of acoustic system, two kinds of cross-correlation methods (the direct correlation method and the M-sequence modulation correlation method) were applied. According to the direct correlation method, by using stationary random noise source and by calculating the cross-correlation function between the sourece and the output signal, equivalent impulse response can be obtained not being influenced by the back ground noises. By applying this method, the measurement of echo-time patterns in rooms and oblique incident sound absorption characteristics of sound absorbing materials was carried out. In the case of the M-sequence modulation correlation method which was contrived by Aoshima, an intermittent random nosie modulated by M-sequence signal is used as the source signal, and the cross-correlation function between the M-sequence signal and the squared output signal is calculated. According to this method, equivalent energy impulse response (squared impulse response) of te propagation system can be obtained without being influenced by the back ground noises and the air fluctuation caused by wind. As the applcaition of this measuring method to the architectural acoustics, the meaurements of echo-time patterns, reverberation decays and sound pressure lev디 distributions in rooms and sound insulation efficiencies in buildings were carried out. From these experimental studies, it has been found that this M-sequence modulation correlation method is markedly useful especially for the field masurement of sound insulation under high back ground noise condition.

음향전파 측정에 상호상관법(직접법과 M계열 변조상관법)을 이용하므로서 임펄스 입력에 의한 경우와 같은 결과를 얻을 수 있다는 것과, 또 상호상관법의 특징인 외란노이즈의 영향을 줄일 수 있었던 것 등을 건축음향분야에서 측정계를 대상으로 하여 이론적으로 정리하였다. 또 이들 계측법을 응용하여 흡음재료의 사입사 흡음특성의 측정, 실의 단독 단음응답 및 잔향감쇄 과정의 측정, 음압레벨 분포, 차음성능 등을 측정하고 여러 건축음향측정에서 이들 방법이 유효하다는 것을 실험적으로 확인하였다.