Improvement of sound transmission loss of single wall acoustic metamaterial using Helmholtz resonator with tapered neck.

Abstract

In previous researches, acoustic metamaterial plates, in which Helmholtz resonators are periodically included in a glass plate at intervals of a wavelength or less, improve the sound transmission loss (TL) at 2.1 kHz. However, the human ear is sensitive to sounds at 2 kHz and higher, and further improvement of TL is essential. In this study, we will improve the TL at 2.1 kHz by changing the shape of the neck of the Helmholtz resonator from cylindrical to tapered. The volume of the neck of the resonator is the same as the cylindrical shape, and the length of the neck and the radius of both ends are changed. The numerical analysis using the finite element method makes a TL comparison of the resonator with a cylindrical neck and a tapered TL.