ON THE USE OF HELMHOLTZ RESONATORS AS SOUND ATTENUATORS

In the present paper a nonlinear acoustic theory is proposed, to accur ately describe the properties of a generalized type of Helmholtz reson ators. The theory may be used as a layout tool to design sound attenua tors for combustion facilities. The present investigation shows that, in addition to the nonlinear effects, the effects due to thermoacousti c boundary layers and the first frequency correction to the ''Helmholt z approximation'' should be taken into account, in order to predict th e frequency-dependent attenuation properties of Helmholtz attenuators with the accuracy required by typical technical applications. A series of experiments is presented which is used to validate the theoretical predictions.