テーパ部のある挿入管形消音器の透過損失

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This paper describes the transmission loss (TL) of the expansion chamber silencers each with an inserted tube and a tapered section. In the duct system used for the experiment, the nonreflected acoustic tube constructed by connecting a conical tube and an involute tube with glass wool was attached to the end of the main duct. The difference between the maximum and minimum values of the acoustic standing waves measured on each frequency by sliding the probe tube microphone in the flow duct was very small except low frequency. It was found that the TL of silencers with flow was able to be measured with high accuracy at the frequency above 200 Hz, using the above mentioned equipment and method. The TL values measured for the silencers tested agreed fairly well with the values calculated on the basis of plane wave and conical horn theory in the range of center velocity in the duct less than 50 m/s at least, so far as they were independent of the flow noise generated secondarily in the silencers. The prediciton of TL characteristics for the tapered types of silencers becoms relatively simple because of the limited influecne of the flow noise on the reducible amount of the primary source noise. These show that the liniear acoustic theory with zero mean flow is of value in designing the expansion chamber types of silencers.
東海大学の論文