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A perforated plate is used as an acoustic absorption material for compressors and acoustic barriers for roads and railways. The effects of the perforated plate on the acoustic natural frequency of an one dimensional sound field partitioned with the perforated plate has been studied in our previous investigations. And it was clarified that the acoustic natural frequency of the one dimensional sound field partitioned with the perforated plate becomes lower as the aperture ratio becomes smaller. There are two methods obtaining the acoustic natural frequencies. One is the method based on the eigenvalue analysis. And the other is the one based on the peak frequency of the response analysis. In this paper, the impedance derived by Melling is used for the response analysis. we compared two acoustic natural frequencies calculated by different two methods. As a result, it was clarified that the acoustic natural frequency calculated by the response analysis was a little smaller than that calculated by the eigenvalue analysis in all conditions. But its difference is small, and both the acoustic natural frequencies calculated by two methods agree with experimental results. And it has become easier to physically understand the analytical and experimental results by considering and comparing the element of transfer matrix.

Study on a method for estimating acoustic natural frequency of one dimensional sound field partitioned by perforated plate