开孔对封闭空间共振特性的影响

研究了开孔对封闭空间声场的影响。通过将孔内振动空气等效为点源,用模态展开法建立了开孔封闭空间的声场模型,计算了开孔封闭空间高阶共振频率和在共振频率激励下的声压分布。结果显示:开孔等效于孔处声质量减小,一般使得开孔封闭空间的共振频率增加;但当孔位于某模态节点时,由于该阶模态与任一模态在开孔处未发生耦合,该模态共振频率不变;由于在开孔区域对应于激励频率的模态声压和其余各阶模态声压之和的相位相反,高阶共振频率激励下靠近小孔位置的声压减小。因此,开孔对封闭空间声场有影响,其影响程度与开孔位置和开孔尺寸有关。

Effect of an aperture on enclosure resonance characteristics

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.