RESONANT PROPERTIES OF SHORT EXPANSION CHAMBERS IN A CIRCULAR DUCT: INCLUDING EXTREMELY SHORT CASES AND ASYMMETRIC MODE WAVE INCIDENCE CASES

Resonant properties of short expansion chambers are studied comprehensively using a traditional analytical approach with simply refined equations. Containing enough number of radial modes in calculation, properties of chambers including the cases of extremely short ones and/or asymmetric mode waves incidence are investigated, and confirmed experimentally with the well-designed apparatus. For various dimensions of chambers and for any mode wave incidence, resonant properties are simply summarized using the resonant frequency, which is almost decisively normalized by the chamber depth and the wavelength of the plane wave for an extremely short one; and by the chamber diameter for a relatively long one with the transition length from acoustically short (resonant-type) to long (common-type): the length is also decided by the chamber diameter. As the case may be, the extremely short chamber might be applicable as a compact resonator muffler.