Transient modal radiation of axisymmetric sources: application to loudspeakers.Report as inadecuate

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1 ENSTA ParisTech UME - Unité de Mécanique 2 LAUM - Laboratoire d-acoustique de l-université du Maine

Abstract : For high amplitudes of vibrations, loudspeakers are subject to nonlinear phenomena that are responsible for audible distortions. In order to describe the complex dynamics of the system, the displacement ¯eld as well as the radiated sound pressure must be expressed in the time-domain. Thus the present study proposes a transient model of the acoustic radiation of axisymmetric structures. The pressure ¯eld is approximated by the Rayleigh integral corresponding to a monopole source distribution over the non-planar vibrating surface. The displacement ¯eld is expanded on the linear modes of the structure and a change of variables in the Rayleigh integral is then proposed in the case of a monotonic pro¯le function to compute the Spatial Impulse Response associated to each mode of vibration e±ciently. The results are compared to the formulation obtained in the case of planar and spherical sources. The method of calculation is then derived in the case of a typical loudspeaker pro¯le association of a truncated cone with a spherical cap. Finally, the present approach is used to estimate the nonlinear radiation pattern of a prototype loudspeaker and predictions are compared to measurements in anechoic room.

Author: Nicolas Quaegebeur - Antoine Chaigne - Guy Lemarquand -



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