LMA - Laboratoire de Mécanique et d’Acoustique

T. Bravo - Micro-capillary plate absorbers for broadband dissipation in the low frequency range

visioconférence

Le 9 février 2021 de 11h00 à 12h00

Maria Teresa Bravo, Consejo Superior de Investigaciones Científicas / Instituto de Tecnologías Físicas y de la Información “Leonardo Torres Quevedo”

Abstract Dissipation of unwanted acoustic contamination at low frequencies is difficult by traditional methods because of the dimensions and weight required. Micro-Perforated Panels have been developed as efficient sound absorbing structures constructed without porous materials. To achieve optimal and broadband performance in the low frequency range, the holes diameters should be diminished to the order of the micrometric scale. Micro-capillary plates (MCPs), typically used as image intensifiers or photo-multipliers in Velocimetry Laser Doppler, constitute an alternative to traditional micro-perforated panels as compact acoustic absorbers. In this work, their acoustic performance is studied by considering two different regimes, the continuous approach and the slip-flow regime. The analytical predictions are verified experimentally in laboratory conditions for both unbacked and rigidly-backed MCPs under normal plane wave incidence and in the no-flow case. These studies showed the ability of unbacked optimal MCPs to achieve absorption values greater than 0.7 up to 6.7 kHz with a flat absorption plateau of 0.86 up to 1 kHz under normal incidence. The test results show good agreement between theory and experiments and confirm the suitability of the proposed devices for low frequency noise dissipation and controlled anechoic terminations for transmission tubes.

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