Modeling Autler-Townes splitting and acoustically induced transparency in a waveguide loaded with resonant channels

We study acoustic wave propagation in a waveguide loaded with two resonant side-branch channels. In the low-frequency regime, one-dimensional models are derived in which the effect of the channels are reduced to jump conditions across the junction. When the separation distance is on the scale of the wavelength, which is the case that is usually considered, the jump conditions involve a single channel and acoustically induced transparency occurs due to out-of-phase interferences between the two junctions. In contrast, when the separation distance is subwavelength, a single junction has to be considered and the jump conditions account for the evanescent field coupling the two channels. Such channel pairs can scatter as a dipole, resulting in perfect transmission due to Autler-Townes splitting. We show that combining the two mechanisms offers additional degrees of freedom to control the transmission spectra.