Coupled Helmholtz resonators for acoustic attenuation

Helmholtz resonators are used in a variety of applications to reduce the tr ansmission of unwanted sound. This work demonstrates that mechanically coup led resonators can be used to design a particular transmission loss respons e, provide a wider bandwidth of attenuation, and adapt the transmission los s characteristics of a structure to attenuate disturbances of varying frequ ency. An analytical model is developed for a single, coupled resonator syst em mounted on a one-dimensional duct. Experiments are conducted on a simila r system that uses a thin membrane to couple the resonator volumes. A simpl istic model of the membrane is presented to estimate equivalent "piston" pr operties from measured physical properties. Experirments confirm that the c oupled resonator system behaves as predicted by the model simulations, and that the transmission loss can be shaped by adjusting the mass or stiffness of the coupling member. The experimental results also illustrate the struc tural-acoustic coupling effects bmr rm the resonators and the membrane, and indicate that a more inclusive model of the membrane and acoustic dynamics is required in order to accurately predict the resonator transmission loss .