A Modal Analysis of Violin with Nearfield Acoustical Holography.

我们发展了一种利用近场声全息术从表面辐射的声学数据测量表面速度的方法。我们首先通过数值模拟和高频降维实验考察了数据采集的参数，从而正确地重建了振动表面。它们是平面位置、数据采集区域和采样间隔。然后利用实验结果对小提琴顶板的振动进行了实验测量。用振动工具对其进行振动，并在靠近平板的平面上测量辐射压力场。由这些数据重建了板的速度，其节线与Chladni法得到的节线几乎相同。这意味着我们的方法是可靠的。这种方法的分辨率不到波长的百分之一，因为可以在335赫兹的“环形模式”下重建出约7 mm宽的f孔，其中波长大于1m。这些结果将在国际声学研究和教育研讨会(ASVA‘97)上公布。

We have developed a method using nearfield acoustical holography to measure velocity of a surface from the acoustic data radiated from it. We examined at first the parameters of the data acquisition by the numerical simulation and the experiment in the reduced size with high frequency to reconstruct properly the vibrating surface. They are the position of the plane, data acquisition region and the sampling intervals. Then using the results we have experimentally measured the vibration of a violin top plate. It is shaken by a vibration-tool and the radiated pressure field is measured on a plane near the plate. The velocity of the plate are reconstructed from the data, of which the nodal lines are almost the same of those once obtained by Chladni method. This means that our method is reliable. The resolution of the method is less than a hundredth of the wave length, because the about 7 mm width of the 'f-hole' of the plate could be reconstructed in the 'ring mode' of 335 Hz, of which wavelength is more than 1 m. These results will be presented at International Symposium on Simulation, Visualization and Auralization for Acoustic Research and Education (ASVA'97).