Objectives  In view of the poor sound insulation performance and pressure resistance of anechoic layer with single cavities at low frequencies, the finite element software COMSOL is used to calculate the acoustic performance and deformation of a combined cavity structure under hydrostatic pressure.

  Methods  Comparing the results of the COMSOL simulation with the experimental data, the validity of COMSOL in calculating the sound transmission loss and absorption coefficient of an anechoic layer is verified. Then, the effects of the geometrical size of the combined cavity and the hole structures on the sound insulation, sound absorption and pressure resistance are studied.

  Results  The results show that the larger the effective cavity volume of the anechoic layer, the better the sound transmission loss performance of the anechoic layer at low frequencies and the worse the sound absorption performance at high frequencies. However, the larger the distance between adjacent cavities, the lower the sound transmission loss of the sound insulation material at low frequencies. The influence of the cavity within the anechoic layer on its pressure resistance is that the larger the volume of the cavity, the worse the pressure resistance becomes. Placing a certain number of cylindrical holes around the combined cavity can improve the sound insulation and absorption performance at low frequencies, and make the peak frequency shift to a lower frequency.

  Conclusions  Therefore, the selection of the volume of the combined cavity needs to consider the balance between the low frequency sound insulation and the pressure resistance. The arrangement of the cylindrical holes around the combined cavity can also improve the low frequency acoustic performance of the anechoic layer.