This report studies theoretically and experimentally acoustic non-reciprocity in a nonlinear asymmetric 1D vibro-acoustic system, featuring two dissimilar acoustic waveguides coupled through a vibrating membrane, and connected by four acoustic cavities. The large-amplitude membrane vibrations induce strong stiffness nonlinearity, while the unequal lengths of the waveguides and the different volumes of the acoustic cavities introduce asymmetry. Hence, the prerequisites for passive break of reciprocity are satisfied in this system. A reduced order model (ROM) is constructed in the form of a three DOF system of coupled oscillators, and its monochromatic steady-state responses subject to forward or backward harmonic sound excitations are analyzed by the Complexification-Averaging (CX-A) method. The stability analysis of these solutions reveals the existence of saddle-node and Hopf bifurcations and the prediction of quasi-periodic responses for forward sound transmission, but not for backward. The CX-A predictions are fully verified by direct numerical simulations of the ROMs, demonstrating steady-state non-reciprocal acoustic energy transfers in the forward or backward directions. Additionally, simulations of the free decay responses of the ROMs verify non-reciprocal vibro-acoustics in the absence of external excitations and reveal the relationship between non-reciprocity and the nonlinear normal modes (NNMs) of the underlying undamped and unforced system. The theoretical findings are fully verified by experimental measurements, proving non-reciprocal sound transmission in forward and backward directions, and demonstrating that uni-directional sound transmission in preferential directions can be achieved in practical coupled waveguides. The methodology discussed in this work can be used for designing and realizing practical non-reciprocal vibro-acoustic systems with directional sound transmission.

Dr. Jiangming Jin received the Ph.D degree from the Zhejiang University, China in 2010. From 2010 to 2012, he joined in Zhejiang University of Technology, China as a postdoctoral research fellow and continuing his research on Nearfield Acoustic Holography. Since 2012, he has belonged to the faculty of College of Mechanical Engineering, ZJUT. From October 2018 to 2019, he was a research fellow in Linear and Nonlinear Dynamics and Vibrations Laboratory, University of Illinois Urbana-Champaign, US. His research interests are Nearfield acoustic holography, Nonreciprocal acoustic wave propagation and Nonlinear dynamic. He has published more than 20 international refereed journals and conference papers.