Nonreciprocal Sound Propagation via Cascaded Time-Modulated Slab Resonators

In this work, we demonstrate nonreciprocal acoustic wave transmission in two-cascaded Fabry-Perotlike slab resonators undergoing time modulation of their effective density. A phase difference is introduced into the time modulation between the two coupled resonators to produce spatial bias to access unidirectional wave propagation. A theoretical model based on plane-wave expansion and the transfer-matrix method is developed to study the Fabry-Perot-based system. The theoretical model allows rapid and precise characterization of the acoustic dispersion, with results in excellent agreement with finite-elementbased numerical simulations. We demonstrate acoustic nonreciprocity behavior for the fundamental acoustic mode and further show that, with proper optimization, the coupled Fabry-Perot-based device can achieve nonreciprocal acoustic frequency conversion. This work could inspire the design of simple and compact nonreciprocal acoustic devices for efficient wave control.

Automated summary

This work demonstrates nonreciprocal acoustic wave transmission in two-cascaded Fabry-Perot-like slab resonators through time modulation of their effective density, introducing a phase difference between the two coupled resonators to enable unidirectional wave propagation. A theoretical model based on plane-wave expansion and transfer-matrix method accurately predicts the acoustic dispersion and shows excellent agreement with numerical simulations. The optimized coupled Fabry-Perot-based device can achieve nonreciprocal acoustic frequency conversion, inspiring the design of simple and compact nonreciprocal acoustic devices for efficient wave control.