Hybrid passive-active multilayer sound absorbersActa Acustica (2003)
AbstractA two-layers passive/active system to afford broadband absorption, including low frequencies, is described. A two layers system, the first of fibrous material and the second of air, provides passive absorption. To absorb low frequencies, an active controller drives an actuator in the back of the system in order to minimize the pressure picked up by a sensor in the air layer. The passive/active system is modelled considering plane waves propagating at normal incidence. Since low frequencies are of interest, the equations of Allard and Champoux are used to characterize the absorbing layer. Two control conditions are compared for the active system: pressure release and impedance matching. Unlike the Beyene and Burdisso results, our model predict better performance of the pressure release condition for values of R=R1 d/Z0 close to 1.2, being R1 and d the flow resistivity and the thickness of the absorbing layer, respectively, and Z0 the air impedance.
Publication DateMay, 2003
Citation InformationP. Cobo, O. Doutres, A. Fernandez and M. Siguero. "Hybrid passive-active multilayer sound absorbers" Acta Acustica (2003)
Available at: http://works.bepress.com/olivier_doutres/31/