STUDY ON THE SOUND ABSORPTION CHARACTERISTICS OF CORRUGATED MICRO-PERFORATED PANEL ABSORBERS WITH FINITE SIZES

To promote the practical application of micro-perforated panel absorbers (MPA) in engineering, sound absorption performances of corrugated micro-perforated panel absorber (CMPA) with finite sizes were studied in this paper. First, on the basis of the impedance theory of micro-perforated panel, and through coupling the plane wave spectrum method and finite element analysis method, a three-dimensional CMPA model was constructed, which was composed of 15*15 periods, and a set of mathematical formulas calculating sound performances of the model was given under the conditions of normal incidence and oblique incidence of sound waves. Second, the finite element software COMSOL was applied to simulate sound absorption performance of finite periodic CMPA models consisting of unidirectional or bidirectional corrugated panels. And meanwhile, the relationship between the corrugation depth or corrugation pitch and sound absorption performances was analyzed, and the influence of the sound wave incidence direction on sound absorption performances was explored. Finally, to weaken the sensitivity of the sound absorber to the incidence direction of sound waves, a bidirectional CMPA model was designed, and its sound absorption performance was compared with the unidirectional CMPA. The results showed that, compared with the traditional MPA with flat panels, no matter under the normal incident or oblique incidence conditions, the CMPA has better sound absorption performances, including a higher sound absorption coefficient and a wider sound absorption frequency band; compared with the unidirectional CMPA, the bidirectional CMPA can significantly weaken the sensitivity of the sound absorber to the incidence direction of sound wave, achieving effective sound absorption in a larger range of sound wave incidence angles, for example, for an incident sound wave, when its azimuth angle is arbitrary and its incidence angle varies within 0° ~ 45°, the sound absorption coefficient of the bidirectional CMPA is always greater than 0.7 within 500 ~ 2500 Hz.