Experimental investigation on noise reduction by using modified helmholtz resonator

Abstract

Noise is a frequently encountered problem of all the automotive engines. When subjected to external excitation, a Helmholtz resonator can show a strongly resonant response at a well-defined frequency. This resonant characteristic can be used to effectively attenuate the noise, by attaching the resonator to the exhaust. It is particularly useful for the reduction of low frequency and narrow band noise. In this investigation, modified Helmholtz resonators are designed and fabricated by noise frequency spectrum analysis. Modifications of the Helmholtz resonators are carried out by inserting the resonator neck inside the cavity. Noise level by modified Helmholtz resonator at different loading condition of engine was measured. Effect of parallel and series arrangement of resonators on noise reduction was found out. In addition, exhaust back pressure due to the designed resonators was measured to find out its effectiveness. Finally, effect on noise reduction by modified and non-modified Helmholtz resonator was investigated. The results shall enable engineers to know the effect of modified Helmholtz resonator on noise reduction.