Coupled Helmholtz Resonators for Acoustic Attenuation

Abstract

Helmholtz resonators are used in a variety of applications to reduce the transmission of unwanted sound. This work demonstrates that mechanically coupled resonators can be used to design a particular transmission loss response, provide a wider bandwidth of attenuation, and adapt the transmission loss characteristics of a structure to attenuate disturbances of varying frequency. An analytical model is developed for a single, coupled resonator system mounted on a one-dimensional duct. Experiments are conducted on a similar system that uses a thin membrane to couple the resonator volumes. A simplistic model of the membrane is presented to estimate equivalent “piston” properties from measured physical properties. Experiments confirm that the coupled 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 structural-acoustic coupling effects between 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.

Noise control in enclosures: Modeling and experiments with T-shaped acoustic resonators

“…When the internal resistance of the resonator is very small, the acoustic interaction between the enclosure and resonator sharply splits the targeted resonance peak of the enclosure into two parts, and the peak response is significantly attenuated within a very narrow frequency band. 4 By properly increasing the internal resistance of the coupled resonator mode, the working bandwidth of the resonator can be improved, while sacrificing some control performance due to decreased amplitude. However, if the resistance is too large, both the velocity amplitude of the fluid inside the resonator and the strength of volume velocity out of the resonator aperture become too small; such low velocities can only produce low dissipation in the resonators and slight acoustic interaction between the enclosure and resonators and hence result in insignificant control at the targeted enclosure resonances.…”

“…2,3 Noise control using long cylindrical tube-shaped resonators for fairing noise control has also been investigated. 4,5 Despite all the effort, the design of acoustic resonators is still limited by a number of factors. The first one is the lack of theoretical modeling tools to facilitate and optimize the design of such devices for a given enclosure, which actually still involves intensive experimental measurements on a trialand-error basis.…”

“…When properly designed, a passive method using an acoustic resonator can effectively absorb acoustic energy from a targeted acoustic mode. [1][2][3][4][5][6][7][8][9] Ideally, it is desirable to integrate resonators into the host structure to save space, particularly for small enclosures. However, it is difficult to meet this requirement with a classical Helmholtz resonator because of its bulbous profile.…”

Model of the Photoacoustic Helmholtz Resonator with Conical-Ended Duct

“…Helmholtz resonators are used in many applications, e.g., for noise reduction [1,2], acoustic attenuation [3], etc. A very important advantage of the Helmholtz resonator is its relatively small size.…”

Acoustic attenuation performance through a constricted duct improved by an annular resonator

“…The environment would be polluted when the absorbing materials were exposed to flow, 1,2 and the low frequency sound absorption was not effective. For reactive silencers, Helmholtz resonators [3][4][5][6][7] or side-branch resonators, 8 were designed to control noise in a narrow frequency range. Recently, Huang [9][10][11] proposed a drumlike silencer, which was made up of an expansion chamber with two sidebranch cavities covered by light membranes under high tension.…”