Alternations in Helmholtz resonator neck angle and the shape of its connection to the air channels to increase the insertion loss of sound

Different methods of sound control in industry have been investigated by the researchers. The passive methods such as membrane absorbents, porous absorbents and the sound resonators are among the most important methods of sound control and reduction. In the present study, the effects of changing Helmholtz resonator neck angle relative to the sound channel along with the other alternations in geometric properties of the resonator such as length, cross section and the shape of the cross section were investigated. The circular and rectangular necks with various lengths and shape were used for finding the changes of insertion loss in a cylinder shaped channel made out of PVC with 3 m long and diameter of 9 cm and the thickness of 2.7 mm. The level of insertion loss of sound would be higher in comparison with 45 and 90 degree angles. The rectangular shaped neck exhibited the least efficiency in sound reduction while the conical shaped neck whose base attachment to the sound channel has circular shape resulted in highest level of sound dissipation. The shorter necks with larger cross sections, in comparison with longer necks with small cross sections, would lead to higher insertion loss of sound.

Keywords:

Helmholtz resonator , Insertion loss of sound (IL) , Neck angle of resonator , Shape of resonator neck