A method has been developed that allows LAUM to establish a framework of dissipated or produced acoustic energy in a scattering area. This criterion was used in connection with two contracts CIFRE with EDF to build whistling diaphragms. It is now used as part of the European project FlowAirS to exploit experimental results and numerical simulations conducted on various elements (corrugated pipes, double diaphragm). Work on the double diaphragms led to the study of systems with a PT symmetry. For the latter, the absorption and gain are balanced (see figure) and can have a conservative overall behavior.
PT Symmetry device in Acoustics
In many areas of wave physics, the presence of losses was treated as a negative characteristic. Therefore, many efforts have focused on how to minimize them. However, in some cases, losses can lead to interesting and useful non Hermitian wave phenomena. Among them we study the coherent perfect absorption (CPA). Control of the absorption can be accomplished by setting geometrically interaction between resonators (see figure). The approach we follow is not limited to audio, and therefore, our findings could have applications in all areas of wave physics. In particular, the importance of perfect absorption using acoustic resonators regards the sub-wavelength absorbers design. Extension of these non Hermitian concepts in the nonlinear realm including nonlinear CPA and nonreciprocal propagation are under investigation.
Unidirectionnel Acoustic Perfect Absorption