Broadband sound absorption of a hybrid absorber with shunt loudspeaker and perforated plates

Abstract

With the effective couplings between the perforated plates and the shunt loudspeaker, a hybrid absorber of shunt loudspeaker and perforated plates (HSLPP) with multiple resonances is proposed for sound absorption at the mid and low frequencies. The absorption characteristics of HSLPP are investigated analytically and numerically, and verified by experimental measurements using impedance tube. Furthermore, the series–parallel coupling effect is intuitively demonstrated by means of the acoustic energy distribution, and the loss state of each resonance is evaluated by a complex frequency plane method. Besides, the effect of the structure parameters on the sound absorption of HSLPP is analyzed, and the optimal sound absorption of HSLPP is compared with that of classical MPP. The measurement results showed that HSLPP samples with a limited thickness of 100 mm have average sound absorption coefficients higher than 0.9 at 200–1100 Hz over 2 octaves. This indicates that the proposed HSLPP structure is a quasi-perfect and sub-wavelength absorber for broadband sound absorption.