Sound absorption of a shunt loudspeaker on a perforated plate

Abstract

A single loudspeaker has weak sound absorption due to its excessive acoustic resistance and abrupt acoustic reactance when used for large area noise control. In this paper, a SLPP absorber composed of a shunted loudspeaker and a perforated plate is proposed to enhance sound absorption. A lumped parameter theoretical model and a three-dimensional finite element model are established to investigate the sound absorption performance of the SLPP absorber. The potential sound absorption mechanism is the coupling effect of three resonance modes: the electrical resonance of the shunt circuit, the mechanical resonance of the loudspeaker’s diaphragm and the Helmholtz resonance of the perforated plate. To reveal the multi-resonance coupling effect, the sound pressure, particle velocity and loss mode at three resonances are explained using finite element model and complex frequency plane method, respectively. The influence of parameters on the sound absorption of SLPP absorber is discussed, as well as the design process and optimized sound absorption are described. The results show that the SLPP absorber as a passive system can achieve an optimized sound absorption in a specific frequency range. Finally, experimental measurements are conducted in square and circular impedance tubes, in good agreement with the predicted results. It is demonstrated that the proposed SLPP structure is an effective subwavelength absorber for low frequency sound absorption.