2025/03/14 by Maddi, Anis, Poignand, Gaelle, Achilleos, Vassos +2 · 2 citations
#Applied Physics (physics.app-ph) #FOS: Physical sciences #Optics (physics.optics)
paper · doi:10.48550/arxiv.2503.11748
In this study, we experimentally investigate the application of a transient signal with complex frequencies to the absorption and transmission of sound waves. Indeed, the emission of a wave with an exponentially varying amplitude in time is analogous, in the frequency domain, to a monochromatic wave with spatial gain or loss. Our results show that by exciting a non-critically coupled Helmholtz resonator with a wave having a growing amplitude, total absorption can still be achieved. Furthermore, the lossy propagation of a traveling wave in a duct is also studied, and it is shown that the losses embedded in the complex wavenumber can be compensated by using a transient signal with decreasing amplitude. These results confirm the potential of complex frequency excitation for exploring new means of manipulating sound waves to mimic gain and loss.