Experimental investigation of sound absorbers based on microperforated panels

Microperforated panels have been studied as a good, interesting absorbing element. In previous papers the properties of high absorption obtained in a wide frequency band was demonstrated, based on the impedance of the very small perforations. The perforation area ratio, the diameter of the holes, the thickness of the panel, and the density and viscosity of the air are the terms that define the sound absorption provided by the element. The microperforated panels have a simple structure and it is possible to build single or double resonators, in order to obtain a wide band response. An orifice may be considered as a short tube. Many years ago, Rayleigh and Crandall studied the propagation of sound in small tubes, of a very short length compared to wavelength. They found a high acoustics resistance and a very small reactance. So, the microperforated panel can be used as a dissipative element. An experimental investigation was carried out on different samples of microperforated panels, in order to obtain their sound absorption coefficient and so verify the validity of the mathematical models. Microperforated panels have been developed to cover a welding cabin internally, where classical absorbents are useless. (To be presented in Spanish.)