The acoustic localized states and tunneling effects in a tunable resonant cavity system are studied both theoretically and experimentally. The system is composed of two identical onedimensional acoustic phononic crystals (PCs) and the modulated space between them. The space in this system is an acoustic resonant cavity similar to the confined electronic levels in quantum potential barriers. The periodic behaviors of the localized eigenfrequency and the decay factor within the resonant cavity are theoretically derived with some simpler approximation methods, respectively, and also the acoustic tunneling effects for different cavity layers are simulated and explored mathematically. The acoustic resonant cavity which can be adjusted continuously and artificially is structured experimentally. By changing the thickness of the cavity, the tunneling process of acoustic waves through the system is observed, which discloses some periodic differences in the small spectral peaks on the edge regions of the stopbands for different cavity layer thicknesses. There are some discrete transmitted spectra in the stopband region, which indicates the periodic energy coupling process and the tunneling dynamics of acoustic waves through the whole acoustic system. The experimental and theoretical results above are in good agreement.

acoustic phononic crystal; acoustic tunneling effect; acoustic energy coupling