Abstract
Helmholtz resonator is an effective acoustic attenuation device at low frequencies and is generally used as passive damper. In this work, parallel perforated ceramics with different perforation diameters were used to improve acoustic impedance at the entry of the resonator and thus achieve better acoustic absorption coefficient and better absorption bandwidth simultaneously. With experimental measurement, ceramics with different perforation diameters are found to improve sound absorption performance of Helmholtz resonator in different extent. At the same time, a model is developed to calculate the resonator's neck mouth impedance and further to predict sound absorption coefficient. Particularly, resonance resistance is considered based on the nonlinear correction to Darcy's law. The results show that large resonance resistance with large perforation diameter materials are due to non-fully developed factor. The largest velocity oscillation amplitude in the resonator neck will lead the Reynolds number up to more than 3000 near the resonance frequency and thus make the nonlinear Forchheimer revision coefficient decrease as Reynolds number increase. Helmholtz resonator with neck filled with sound absorption materials has improved sound absorption capacity. This prediction agrees well with the experiment results and this model can be used to optimize the sound absorption system with Helmholtz resonators.
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