Abstract
A reactive type silencer like a side branch silencer is effective for the reduction of the sound with periodicity. It is often used to reduce the noise generating the pulsating pressure etc. This is especially effective for the noise with single frequency. However, an effective frequency range is comparatively narrow. Moreover, the silencer is obliged to be large for countermeasure of the low frequency sound. And, that might cause the problem of the installation space. Then, in order to develop the side branch silencer which is effective for the low frequency range, the side branch with the finite impedance at the end of it was made and examined. As a result, it was clarified that this side branch was able to achieve the objectives.
