On the Acoustic Absorption of Multi-Layer Absorbers With Different Inner Structures

Analysis of coir fiber acoustical characteristics

“…Results showed that their technique was more accurate than the conventional method which considers surface acoustic impedance of back airspaces or porous material as rigid wall impedance even when they were actually backed with perforated plate. Moreover, they [22] studied the effects of inner structure of multilayer absorbers on their acoustic characteristic. Results described that having more materials in front or behind the perforated plate will enhance the acoustic absorption at higher and lower frequencies, respectively.…”

Numerical investigation of active porous composites with enhanced acoustic absorption

“…They show that the improvement by distributed masses (inclusions) tend to be greater than the one due to the mass effect alone. The acoustic absorption of multi-layer absorbers with different inner structures has also become a subject of research [2]. The proposed modeling is accurate with respect to the geometry thanks to the finiteelement approach, however, the porous medium is modeled by using the so-called fluid-equivalent approach which generally assumes that the frame (i.e., solid skeleton) of a porous medium is rigid.…”

Analysis on Multiple Perforated Plate Sound Absorber Made of Coir Fiber

“…10 In their further work on multilayer absorbers with different inner structures, they showed that the inner structures influenced the sound absorption at some frequency bands significantly. 11 The quantity of the porous material in front of the outmost layer of PP controlled the absorption at high frequencies. More porous material in front of and behind the PP promoted the absorption at higher and lower frequency bands, respectively.…”