Silencer consisting of two-stage Helmholtz resonator with auto-tuning control

摘要

A Helmholtz resonator has advantages over other noise control methods in that it does not require energy to function and it can be applied to high-frequency noise. In this article, a noise reduction method based on a Helmholtz resonator is discussed in reference to application to a blower. However, as the frequency of noise generated by a blower, although high, varies over time, the Helmholtz resonator is ineffectual if applied directly. In order to reduce varying high-frequency noise, a new type of silencer, comprised of a two-stage rotary auto-tuning resonator, is proposed. A fast Fourier transform (FFT) analysis of noise obtained by a noise meter is used for control The frequencies of the peak intensities obtained by the FFT vary according to the variations in source frequency. Two significant peaks in the frequency domain are considered, the cost functions of which are taken, allowing for frequency variation. The silencer is tuned by minimizing the cost function. THe system and control algorithm are presented in this report, along with the results of experimental tests that were conducted on a typical blower in order to verify the effectiveness of the system and method.