Abstract
Pressure fluctuation occurs in an oil pressure pump in the nature of the machine. It becomes a cause of a vibration and a noise of a building where the oil pressure pump are set because the pressure fluctuation gives a fluctuating force on floors and walls of the building. So it is important to reduce the vibration and noise from an environmental point of view. A side-branch is often used to reduce the pressure fluctuation because of its simplicity and its effectiveness. However the long side-branch is necessary to reduce the low frequency noise because of the relation f=c/4L. Where L is the side-branch length. In this paper, the noise reduction effect of the side-branch with the finite impedance end is examined theoretically and experimentally. As a result, it was clarified that the side-branch with the finite impedance end gives the reduction effect in frequency range lower than that of the rigid end.
