Perfect acoustic absorption in reciprocal ventilated problems

Abstract

This work presents the different possibilities to obtain perfect absorption in reciprocal ventilated problems, i.e., in the situation in which both reflection and transmission are considered. By using the scattering matrix formalism, the perfect absorption is obtained when the critical coupling conditions are fulfilled, i.e., when the two eigenvalues of the scattering matrix are zero at the same frequency and the system is excited with the corresponding eigenvector. These conditions impose that only two types of mechanisms can be used to obtain perfect absorption: (i) breaking the symmetry by using non-symmetric resonators or (ii) maintaining the symmetry, but using degenerate resonators. We show two systems made of Helmholtz resonators presenting perfect acoustic absorption, each based on each solution. The systems are analytically, numerically, and experimentally characterized with a very good agreement between them, thus opening new venues for the design of acoustic treatments at low frequencies.

@inproceedings{RomeroINTERNOISE2021a,
 author = {Vicent Romero-García and Noé Jiménez and Vincent Pagneux and Jean-Philippe Groby},
 booktitle = {EuroNoise 2021: European Congress and Exposition on Noise Control Engineering. Madeira, Portugal. 24-27 October},
 doi = {http://www.sea-acustica.es/},
 editor = {Conference proceedings},
 month = {10},
 organization = {Sociedade Portuguesa de Acústica},
 pages = {1463-1469},
 series = {Oral},
 title = {Perfect acoustic absorption in reciprocal ventilated problems},
 url = {http://www.sea-acustica.es/},
 year = {2021}
}