Abstract: Effect of the cavity volume porosity on sound insulation performance of acoustic material was researched. The results showed that when the spherical cavity sample and the truncated cone sample were of the same cavity volume,the decrease amplitude of the sound insulation performance in the spherical cavity sample was lower than that of the truncated cone one. The sound insulation performance could be improved by applying higher cavity volume porosity under low hydraulic-pressure for the spherical cavity; for the high water pressure,the acoustic material with a 19. 92% cavity volume porosity performed better in sound insulation.