相関法による音圧複素反射係数の実時間ベクトル表示法

概要

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This paper describes a method for displaying the sound pressure complex reflection coefficient Γ of the acoustic panel as a vector directly on the cathode-ray tube in real time by using a correlation technique, and its application to a direct view type measurement of the acoustic properties such as sound absorption coefficient α, acoustic resistance R, acoustic reactance Χ, and absolute value|Γ|and phaseφof Γ. In this method, a cross correlation function between source and receiver signals through a narrow band-pass filter which becomes equivalently a sinusoidal sound wave of time delay is used. And, it is realized to display a vector of Γ in real time by extracting the real part|Γ|cosφand the imaginary part|Γ|sinφof Γ directly from the compound sound wave close to the acoustic panel measured by a correlator using a M-sequence signal and by feeding these two analog values to the vertical and horizontal terminals of the cathode-ray tube. Therefore, it is possible to read each of acoustic properties through complex reflection coefficient chart, sound absorption coefficient chart and Smith chart put on the vector. Experiments in the case of the normal incidence are carried out. Comparing with standing wave method, the validity of this method is shown. But, it is not yet about the case of the oblique incidence.
社団法人日本音響学会の論文
1982-12-25