Thin low frequency sound absorbers based on shunted loudspeakers

Abstract

There are two main reasons for using shunted loudspeakers as sound absorbers. One is that the absorbers can be made very thin for the low frequency sound with electronic energy dissipation mechanism and the other is that their absorption performance can be adjusted with the shunt circuit. A shunted loudspeaker typically has high absorption coefficients around its resonance frequencies which are determined by the loudspeaker unit and the shunt circuit together. To extend the effective frequency range of the shunted loudspeaker, one method is constructing more resonant sub-systems in the absorber to have absorption at more resonance frequencies. In this research, two designs based on shunted loudspeakers will be introduced. One is the composite absorber with a micro-perforated panel in front of a shunted loudspeaker, which combines two resonance subsystems to provide broadband absorption. The other is a shunted loudspeaker with a specifically designed shunt circuit for the absorption of three tonal componen...