Vibroacoustic properties of thin micro-perforated panel absorbers.
This paper presents theoretical and experimental results on the influence of panel vibrations on the sound absorption properties of thin micro-perforated panel absorbers (MPPA). Measurements show that the absorption performance of thin MPPAs generates extra absorption peaks or dips that cannot be understood assuming a rigid MPPA. A theoretical model is established that accounts for structural-acoustic interaction between the micro-perforated panel and the backing cavity, assuming uniform conservative boundary conditions for the panel and separable coordinates for the cavity cross-section. This model is verified experimentally against impedance tube measurements and laser vibrometric scans of the cavity-backed panel response. It is shown analytically and experimentally that the air-frame relative velocity is a key factor that alters the input acoustic impedance of thin MPPAs. Coupled mode analysis reveals that the two first resonances of an elastic MPPA are either panel-cavity, hole-cavity, or panel-controlled resonances, depending on whether the effective air mass of the perforations is greater or lower than the first panel modal mass. A critical value of the perforation ratio is found through which the MPPA resonances experience a frequency "jump" and that determines two absorption mechanisms operating out of the transitional region.
Centro de Acústica Aplicada y Evaluación No Destructiva, Consejo Superior de Investigaciones Científicas, Serrano 144, 28006 Madrid, Spain. teresa.bravo@caend.upm-csic.es
Teresa
T
Bravo
Cédric
C
Maury
Cédric
C
Pinhède
D000042:Absorption; D000162:Acoustics / Q000295:instrumentation*; D000388:Air; D003252:Construction Materials; D004867:Equipment Design; D005160:Facility Design and Construction / Q000295:instrumentation*; D008962:Models, Theoretical; D009038:Motion; D009622:Noise / Q000517:prevention & control*; D016062:Porosity; D011312:Pressure; D015203:Reproducibility of Results; D014732:Vibration