Study on the control of noise reduction in low frequency range for splitter type silencers

A general splitter silencer has mainly noise reduction performance in middle frequency range. Thus, the noise reduction in low frequency range is not enough, even if the silencer has long length. On the other hand, some large fan in a power plant has peak sound power level in low frequency range according to the number of the blades and the rotating speed. We studied low frequency noise reduction of a splitter silencer embedded resonator units by controlling the hole diameter and the pitch of the resonator, air space behind and the resonator position in the silencer. As the results of 800mm length resonator unit, the maximum noise reduction of 15.2 dB at 160 Hz was achieved by controlling the specification of perforated plates. And we applied it to an actual silencer and confirmed the performance.