Sound Absorption of the Absorber Composed of a Shunt Loudspeaker and Porous Materials in Tandem

To investigate the sound absorption of the absorber composed of a shunt loudspeaker (SL) and porous materials (PM) in tandem, the normal absorption coefficients for six samples of different groups of parameters are measured using impedance tubes. It is shown that a composite structure consisting of a porous material, an air layer, a shunt loudspeaker, and an air layer arranged in sequence (PM + Air1 + SL + Air2) has the potential to achieve broadband sound absorption close to three octaves in the frequency range of 200-1600 Hz. To further explore the sound absorption mechanism of "PM + Air1 + SL + Air2", a theoretical model based on the transfer matrix method is established, and a numerical model is built in the pressure acoustic module using COMSOL Multi-physics field software. The sound absorption coefficients and acoustic impedances predicted are in good agreement with those measured. The concerned "PM + Air1 + SL + Air2" with suitable parameters has two distinguishable sound absorption peaks in the low frequency domain and a well sound absorption spectrum similar to that of the porous material layer in the high-frequency domain. The reason for the superior sound absorption performance of "PM + Air1 + SL + Air2" lies in the fact that under the common action of the diaphragm's mechanical vibration, the circuit's damping loss, and the porous material's viscous dissipation, the sound energy consumption is mainly dominated by SL in the low frequency domain and captured by PM in the high-frequency domain.