National Center for Physical Acoustics, The University of Mississippi, One Coliseum Drive, University, Mississippi 38677, USA.
J Acoust Soc Am. 2011 Feb;129(2):597-603. doi: 10.1121/1.3523337.
The purpose of this paper is to report on the suppression of an approximately radial (radially symmetric) acoustic mode by an elastic mode of a water-filled, spherical shell resonator. The resonator, which has a 1-in. wall thickness and a 9.5-in. outer diameter, was externally driven by a small transducer bolted to the external wall. Experiments showed that for the range of drive frequencies (19.7-20.6 kHz) and sound speeds in water (1520-1570 m/s) considered in this paper, a nonradial (radially nonsymmetric) mode was also excited, in addition to the radial mode. Furthermore, as the sound speed in the liquid was changed, the resonance frequency of the nonradial mode crossed with that of the radial one and the amplitude of the latter was greatly reduced near the crossing point. The crossing of the eigenfrequency curves of these two modes was also predicted theoretically. Further calculations demonstrated that while the radial mode is an acoustic one associated with the interior fluid, the nonradial mode is an elastic one associated with the shell. Thus, the suppression of the radial acoustic mode is apparently caused by the overlapping with the nonradial elastic mode near the crossing point.
本文旨在报告通过弹性模式抑制充满水的球形壳谐振器中的近似径向（径向对称）声模式。该谐振器壁厚为 1 英寸，外径为 9.5 英寸，通过外部壁上的小换能器驱动。实验表明，在所考虑的驱动频率范围（19.7-20.6 kHz）和水中声速（1520-1570 m/s）下，除了径向模式之外，还会激发出非径向（径向非对称）模式。此外，随着液体声速的变化，非径向模式的共振频率与径向模式的共振频率相交，并且在交点附近后者的幅度大大降低。这两种模式的本征频率曲线的交点也在理论上进行了预测。进一步的计算表明，虽然径向模式是与内部流体相关的声学模式，但非径向模式是与壳相关的弹性模式。因此，在交点附近，与非径向弹性模式重叠显然导致了径向声模式的抑制。
