Design and fabrication of a laboratory device for demonstration of Helmholtz resonators

Abstract

There is an increasing demand for noise emission reduction in many applications today. These applications include automotive exhausts, fan intakes and exhausts, and air conditioning ducts among many others. One way to attenuate the noise produced by these applications includes the use of a Helmholtz resonator. A Helmholtz resonator, also referred to as a side branch resonator to a duct, is simply a cavity with a known volume connected via a neck to a duct. A simple equation relates frequency and resonator geometry such that the length and cross section of the resonator neck, as well as the volume and shape of the resonator cavity, affect resonator performance. In practice a resonator is made to target a certain frequency of noise, which is to be suppressed. The noise reduction achieved is dependent on the accuracy of construction of the resonator. A laboratory setup was constructed which incorporated many of the most influential variables. This setup will be used as a demonstration device as well as a laboratory apparatus in the Mechanical Engineering curriculum at Western Michigan University.