Effect of Perforated Plate on Natural Acoustic Frequency of One Dimensional Sound Field Partitioned by Perforated plate

Kunihiko Ishihara, Satoru Kudo

In previous studies, the natural acoustic frequency of an one dimensional duct partitioned by a perforated plate was clarified to come down with decreasing aperture ratio experimentally and analytically. The natural acoustic frequencies calculated by the Transfer Matrix Method are in good agreement with those obtained by the experiment and the natural acoustic frequency becomes lower with decreasing aperture ratio of the perforated plate. After this study, we calculated the mode of the duct with the perforated plate and focused the shape of the mode. Then the mode shape becomes the sine wave after the particle velocity passing through the perforated plate. The frequency was calculated by the 1/4 wave length of the mode and the frequency was compared with the experimental value. The both values coincide with each other. In this study, the sound propagation experiment was conducted in order to clarify the reason. As a result, it was clarified that the smaller aperture ratio was the longer the sound arrival time became. This is equivalent to the getting long of the duct and the natural acoustic frequency can be considered to become low.