Design optimization for broadband sound insulation by double-panel structure with a slot-type Helmholtz resonator array at low frequency range

In this paper, a numerical study is conducted to optimize the double-panel structure with a locally resonant sonic crystal for the band reduction of the low-frequency sound transmission. Recently, we proposed one type of sonic crystal with slots elongated into the cylindrical shells, namely, the slot-type Helmholtz resonator array. The results indicated that it had the potential to form and broaden the low-frequency band gap. First, the ranges of the slot length and width are determined to form the resonant peak in a given frequency range using the finite element simulation. Next, the optimizations using the Monte Carlo method are performed for the incidences of the plane waves with a uniform and non-uniform spectral densities. It is found that the weighted single-objective optimization proposed can bring out the improvement of the overall sound insulation (10.5 dBA in our case) as well as the elimination of the transmission peaks.