Thermoacoustic parity-time symmetric system
Résumé
Parity-time (PT) symmetric systems have attracted significant attention due to their unusual scattering properties like lossless propagation, unidirectional invisibility or coherent perfect absorption. In acoustics, such systems can be designed with a properly balanced distribution of loss and gain along a waveguide. While losses can be quite naturally introduced, mechanisms to produce gain, in the form electroacoustic circuits or hydrodynamic-sound interactions, require more attention. In this study, we explore the possibility to use thermoacoustic amplification to produce the requisite gain. The whole device is composed of a waveguide equipped with a loss and gain units, both consisting of Helmholtz resonators. The gain unit contains a differentially heated material, heart of the thermoacoustic effect. Two control parameters allow for a fine adjustment of the balance of the gain and the loss in the device: the compliance length of the loss unit changes its reactance, while the temperature gradient along the heated material alters the resistance of the acoustic gain unit. In this talk, both theoretical and the first experimental results will be presented.