THEORETICAL AND EXPERIMENTAL STUDY OF PLANE WAVE PROPAGATION IN ASYMMETRICAL RECTANGULAR WAVEGUIDE FILTERS

摘要

A first type of acoustical waveguide filter, mad eof identical cavities, was developed and studied thoroughly. The noise control performance of that device was limited to a narrow frequency band. A new type of waveguide filter, made of rectangular cavities of different sizes, is proposed in order to extend the band of frequencies for which noise reduction occurs. Furthermore, recent studies, revealing the highly anisotropic behavior of the device, suggested that its performance would improve greatly if the incidence of the acoustic waves was kept normal to the inlet slit of the device. This paper is, therefore, concerned with a theoretical two-dimensional study of plane wave propagation in such a device. The mathematical model used was originally used in the field of microwave propagation in waveguides, where good theoretical prediction was obtained. The sound pressure level and phase differences between two points are evaluated with the theoretical model and compared with experimental values. The theoretical and experimental results are in good agreement. Observations on the effective extension of the pass-band region are presented. [References: 15]