Sound Enhancement of Orthotropic Sound Radiation Plates Using Line Loads and Considering Resonance Characteristics

Ahmad Nayan,Tai Yan Kam

doi:10.3390/acoustics3040041

Abstract

A new vibro-acoustic method is presented to analyze the sound radiation behavior of orthotropic panel-form sound radiators using strip-type exciters to exert line loads to the panels for sound radiation. The simple first-order shear deformation theory together with the Ritz method is used to formulate the proposed method that makes the vibro-acoustic analysis of elastically restrained stiffened orthotropic plates more computationally efficient than the methods formulated on the basis of the other shear deformation theories. An elastically restrained orthotropic plate consisting of two parallel strip-type exciters was tested to measure the experimental sound pressure level curve for validating the effectiveness and accuracy of the proposed method. The resonance characteristics (natural frequency and mode shape) detrimental to sound radiation are identified in the vibro-acoustic analysis of the orthotropic plate. For any orthotropic sound radiation plate, based on the detrimental mode shapes, a practical procedure is presented to design the line load locations on the plate to suppress the major sound pressure level dips for enhancing the smoothness of the plate sound pressure level curve. For illustration, the sound radiation enhancement of orthotropic plates with different fiber orientations for aspect ratios equal to 3, 2, and 1 subjected to one or two line loads is conducted using the proposed procedure. The results for the cases with two line loads perpendicular to the fiber direction and located at the nodal lines of the major detrimental mode shape may find applications in designing orthotropic panel-form speakers with relatively smooth sound pressure level curves.

Highlights

In the audio industry, composite plates have been used to fabricate panel-form speakers for sound radiation
In view of the evolution process involving the vibration shapes at different excitation frequencies as given in Table 1, it is easy to notice that the vibration shape associated with the sound pressure level (SPL) dip is evolved from the mode shape at 3083 Hz when the plate is excited by the two line loads
A new vibro-acoustic method formulated on the basis of the simple first-order shear deformation theory and first Rayleigh integral has been presented to study the sound radiation behavior of elastically restrained rectangular orthotropic sound radiation plate excited by strip-type exciters

Summary

Introduction

Composite plates have been used to fabricate panel-form speakers for sound radiation. The proper excitation locations of two line loads that can enhance the smoothness of the SPL curves of panel-form composite sound radiators with different aspect ratios and fiber angles are determined using the proposed method.

Results

Conclusion