Teresa Bravo, Cedric Maury
Tecniacústica 2023
Del 18 al 20 de octubre de 2023, Cuenca, España.
Attenuation of low frequency noise constitutes a long stating problem in the field of noise control. The use of Micro-Perforated Panels has been proved to be efficient if the primary noise source spectrum is confined in a narrow frequency band. To get rid of the limitations due to the backing cavity depth, unbacked configurations have also been considered. They are able to supply good attenuation results if the size of the hole diameters is reduced and the perforation ratio is increased. These devices are denoted Micro-Capillary Plates. These ultra-perforated membranes consist of highly porous panels made up of leaded glass, of high porosity with millions of micro-channels per centimeter square, the holes or square channel dimensions varying between 5µm and 50µm. They are 1-2 milimeters thick and can be produced in various shapes using drawn tubes of fused, chemically etched fibers, working on both backed or unbacked configurations. These characteristics provide them with exceptional acoustical properties compared to other classical absorbers or MPPs. If rigidly backed by an air cavity of 24 mm, a MCP device provides a half-bandwidth absorption over 12 octaves whereas a MPP device works only over one-two octaves. Their performance will be examined in ducted propagation conditions.
