Abstract: The effects of apertures on the sound field of an enclosure are investigated in this paper.First,the acoustic model of the enclosure with apertures is developed based on the modal expansion approach by considering the vibrating air in the aperture as an equivalent point source,and then the proposed model is used to calculate the higher-order resonance frequencies of the enclosure and the sound pressure distribution at resonance frequencies.The results demonstrate that having an aperture is equivalent to reduction of the acoustical mass at the location of the aperture and generally makes the resonance frequencies of the enclosure increase.If the aperture is located at a modal node,the mode is not coupled with other modes over the aperture,so its resonance frequency remains unchanged.Reduction of sound pressure in the region near the aperture is also observed,which is due to the opposite phases between the modal sound pressures corresponding to the resonance frequency and the sum of the other modal sound pressures.In conclusion,the sound field in an enclosure is affected by the presence of the aperture and the variation degree of the sound field characteristics depends on the location and the size of the aperture.