Helmholtz resonator is often used to reduce noise. This has been especially practical when the noise has significant frequency band. The narrow band characteristics of the resonator is what has known to be what can not be changed or even improved.
This study aims to broaden the narrow band characteristics of the resonator. Serial and parallel arrangement of resonators have been tested to obtain high transmission loss characteristics in the broader band. Theoretical and experimental results explain these characteristics in the absence of any mean flow.
The change of acoustic characteristics is explained by using the equivalent impedance analysis. The resistance change of resonator’s impedance affects its transmission loss. It shows that the transmission loss has maximum value when the distance of resonators is λ/4 (λ :wave length) of its frequency. As a result of this analysis, silencer must have a long length for having effective noise control at low frequency.
Therefore this study proposes a new design method that optimizes the arrangement of the resonators by keeping the volume unchanged. We can obtain the various transmission loss characteristics when we select different objective function under the constraints.
This optimization method explains that it is possible to design transmission loss shape.
