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Perforated pipe is an essential component in contemporary automotive mufflers, since such a pipe reduces the acoustic power of the flow noise, which is significantly influenced by its velocity. Nonuniformly perforated pipes, the orifices of which are arranged in a belt configuration, are widely used in muffler systems. The resonance of such perforated pipe when located inside the elliptic cavity is investigated experimentally in this paper. The results obtained are also compared with the predictions of our method of theoretical analysis for a uniformly perforated pipe in order to clarify the resonance mechanism. It was found that the difference between the measured and theoretical values is less than 5 Hz for a short pipe. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 85(7): 22–28, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.1104

Perforated pipes are frequently used to attenuate exhaust noise in contemporary automotive mufflers. Resonances at a particular frequency, however, may exceed the overall acoustic reduction effect of the muffler when the shape and fixing position are inappropriate. The theoretical calculations of the sound pressure inside the elliptical perforated tube muffler are carried out by solving the wave equation. The resonance mechanism of the perforated tube muffler is analyzed. The results of the analyses have been confirmed by experiments. © 2000 Scripta Technica, Electron Comm Jpn Pt 3, 83(8): 51-60, 2000