Modifications of acoustic modes and coupling due to a leaning wall in a rectangular cavity

Abstract

Acoustic modes and the coupling characteristics of a rectangular-like cavity with a slight geometrical distortion introduced through a leaning wall are investigated in this paper. A pressure variation index is proposed to quantify the global changes in acoustic modes caused by the inclination of the wall. Effects on the coupling between acoustic modes and structural modes are investigated using coupling coefficients. Numerical results show a simple relationship between the distortion effect and the acoustic wavelength. The effect is most significant when the distortion approaches the half wavelength. Compared with a rectangular enclosure, the existence of the leaning wall gives rise to a much more effective coupling between the structure and the enclosure.

Vibro-acoustic analysis of a rectangular-like cavity with a tilted wall

“…Focusing on those cavity modes, it can be seen that within the analyzed frequency range [0 600]Hz, the left-shift of peaks occurs except for modes (0, 0, 1) and (0, 0, 2), and the variation is getting larger when a increases. The reason is that an increased a alters the dimension of the cavity in x-direction, leading to an increase of wavelengths k lmn and a corresponding decrease of acoustic natural frequencies f lmn (l 6 ¼ 0, c/f lmn = k lmn ) [18]. However, the effect of the wall inclination on the structural modes is trivial.…”

“…Again, no attention was paid to the effect of wall inclination on the vibro-acoustic behavior of the whole system. This paper is a continuation of that work [18] and attempts to provide some answers to this problem. A model is first developed to handle the full vibro-acoustic coupling of a vibrating plate backed by an acoustically hard-walled enclosure with a tilted wall, which is introduced to represent the geometrical distortion.…”

“…All aforementioned works, however, mainly focused on the prediction of the natural frequencies of cavities and seldom addressed the coupling issue and the possible effects of the geometrical irregularity on system responses. A first attempt was made by extending the combined integro-modal approach to analyze the coupling characteristics between a vibrating panel and an irregular-shaped cavity with a tilted wall [18]. Using the coupling coefficients, effects on the coupling between acoustic modes and structural modes were examined, and it was found that the geometric distortion may dramatically change the coupling nature to thwart the prediction using perfect model.…”

A variational formulation for vibro-acoustic analysis of a panel backed by an irregularly-bounded cavity

“…The first nine natural frequencies of the considered enclosure obtained by using present method are given and compared with the exact solutions from Eq. (22) in Table 1. Note here that the zero frequency concerning the rigid-body acoustic mode is omitted from the results.…”

Geometrical perturbation of an inclined wall on decay times of acoustic modes in a trapezoidal cavity with an impedance surface

“…The technique has been successfully used in various studies of sound fields in irregular enclosures. [14][15][16][17] But, all these works only focused on the prediction of resonance frequencies and sound pressure distributions or mode shapes in the enclosures. The same acoustical properties were also of concern even in those investigations using finite element and boundary element methods or direct numerical calculations.…”