Hybrid passive-active absorption of a microperforated panel in free field conditions.
Although hybrid passive-active absorption in impedance tubes has been widely analyzed, its study in more realistic conditions remains to be accomplished. This letter describes the practical measurement of the passive-active absorption coefficient in a free field. The passive absorber consists of a microperforated panel backed by an air cavity and a wooden panel. A multichannel active system controls the sound pressure in a reduced cell behind the absorber. Measured absorption coefficients between 200 and 400 Hz account for 0.2-0.4 and 0.72-0.75, in the passive and active cases, respectively, and above 500 Hz both are comparable.
Cobo
Pedro
P
Instituto de Acústica, CSIC, Serrano 144, 28006 Madrid, Spain.
Cuesta
María
M
D006309:Hearing; D006801:Humans; D009622:Noise; D015203:Reproducibility of Results; D013016:Sound