半空间内结构声辐射研究

采用解析方法,以脉动球为例研究了以自由表面或刚性表面为界的半空间内的声辐射问题.重点研究了自由表面或刚性表面对结构辐射声功率和辐射方向性的影响.数值结果表明:在低频和自由表面距离脉动球源较近时,自由表面的存在会大大地减小脉动球源的辐射声功率,自由表面对辐射声功率的影响可高达-40dB左右.但随着频率和自由表面离脉动球源距离的增大,自由表面对脉动球源辐射声功率的影响会急剧地减小.当频率较高或自由表面距离球源较远时,自由表面对脉动球源辐射声功率的影响是不大的;刚性表面对脉动球源辐射声功率的影响远远小于自由表面对脉动球源辐射声功率的影响,其最大的影响也仅为 3dB.文中还讨论了用边界元法求解三维复杂结构在半空间内的声辐射问题,并进行了计算验证.

Research on acoustic radiation in a three-dimensional half space

Many acoustic problems involve half-space domains bounded by a rigid or free surface.This paper is concerned with the acoustic radiation in a three-dimensional half space.The effects of the rigid or free surface on acoustic power and radiation directivity radiated by a pulsating sphere are analytically studied.It is shown that the free surface may achieve a 40dB reduction in the acoustic power in the very low frequency range when the free surface is very near the sphere. However, the effect of the free surface on the acoustic power is insignificant when the surface is far away from the sphere or the excitation frequency is in the high frequency range.The maximum achievement of the rigid surface is a 3dB increase in the acoustic power. The boundary element formulation for half-space acoustic radiation problems is also discussed and validated.