Development of Shape of Helmholtz Resonator Cavity for Attenuation of Low Frequency Noise of Pure Reactive Muffler
The cut off frequency and the transmission loss measurement with different shape of Helmholtz resonator is observed with muffler is thoroughly investigate in this research work to attenuate low frequency noise by using wave 1 D. A reactive muffler is important noise control element for reduction of exhaust noise. Mufflers are arranged along the exhaust pipe as the part of the exhaust system of an IC engine to reduce its noise. But the attenuation of low frequency noise in muffler is not effective; therefore a cavity called Helmholtz Resonator is attached at the inlet of muffler which is capable to attenuate particularly low frequency noise coming from exhaust. Helmholtz resonators are often used to have control steady, simple harmonic sound field that have tonal, narrow band spectrum. For the high tuned Helmholtz resonators, it is found frequency shifted to a lower resonance frequency in combination with reduced quality factor. Quantification results of transmission loss measurement by using 1 DOF Helmholtz resonator shows the good agreement with the numerical results. It can measure the performance of Muffler's Transmission loss. The resonator attenuates the noise level at low frequency zone and also increases average transmission loss. This study is concentrated on the modeling of Helmholtz type resonator with along with different cavity shape like cylindrical, conical and Spherical of a fixed volume for attenuation of first cut off frequency found in muffler. This attempt gives the proper geometry selection approach for further study. Finite element analysis tools comsol multiphysics and wave 1 D and 3 D module used to validate the results. The results show interesting fact that resonator not only attenuate a particular low frequency noise on muffler and also increases transmission loss which is very effective.