A new Helmholtz type sonic crystal for wide-band sound attenuation

In this paper, a Helmholtz shape sonic crystal is proposed for bandgap realization and sound attenuation. Using Bloch’s theory, bandgap properties of the sonic crystal are investigated for the primitive design of the unit-cell. A geometrical parametric study is implemented for the unit-cell to present its potential in creating bandgaps over the low-frequency range, and an optimization is applied to find its best design according to the low-frequency objective function. A frequency analysis and experimental tests are used to verify the calculated bandgaps from Bloch’s theory and to confirm the sound attenuation ability of the proposed design. It is shown that the present design not only creates wide bandgap frequencies in the low-frequency range but also, due to the Helmholtz shape of the unit-cell, provides significant sound attenuation.