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Closed Access item Measuring hybrid passive-active sound absorption of a microperforated liner at oblique incidence

Authors:Cobo, Pedro
Cuesta, María
Keywords:Acoustic wave absorption, Architectural acoustics, Noise abatement, Reverberation
Issue Date:Jan-2009
Publisher:Acoustical Society of America
Citation:Journal Acoustical Society of America 125(1): 185-190 (2009)
Abstract:The performance of hybrid passive-active absorbers at normal incidence has been previously demonstrated. However, their feasibility in realistic environments remains to be confirmed. This paper proposes a hybrid passive-active liner absorbing at oblique incidence. The passive absorber is a 2.44×2.44×1 mm3 microperforated panel backed by a 5 cm deep air layer and a rigid ending. An active multichannel cell, composed of five single-input single-output controllers, releases the sound pressure at the entrance of the air cavity in a reduced area of the microperforated panel absorber. Hybrid passive/active absorption of the prototype is measured in an anechoic room up to a maximum incidence angle of 21°. For instance, at 20° such a system is able to provide an average absorption of 94% between 266 and 1500 Hz. In addition, the performance that would provide such a hybrid absorber in a reverberant room has been quantified theoretically by an index describing the active-to-passive reverberation time ratio in terms of the active-to-passive absorption area and absorption coefficient ratios. The proposed prototype, implementing 7% of the active proportion area, would afford a reverberation time reduction between 77.5% and 12% from 100 to 500 Hz.
Description:6 pages.-- PACS: 43.55.Ev; 43.50.Ki
Publisher version (URL):http://dx.doi.org/10.1121/1.3026328
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