Huber Thomas M, Fatemi Mostafa, Kinnick Randy, Greenleaf James
Physics Department, Gustavus Adolphus College, Saint Peter, Minnesota 56082, USA.
J Acoust Soc Am. 2006 Apr;119(4):2476-82. doi: 10.1121/1.2171516.
The goal of this study was to excite and measure, in a noncontact manner, the vibrational modes of the reed from a reed organ pipe. To perform ultrasound stimulated excitation, the audio-range difference frequency between a pair of ultrasound beams produced a radiation force that induced vibrations. The resulting vibrational deflection shapes were measured with a scanning laser vibrometer. The resonances of any relatively small object can be studied in air using this technique. For a 36 mm x 6 mm brass reed, displacements and velocities in excess of 5 microm and 4 mm/s could be imparted at the fundamental frequency of 145 Hz. Using the same ultrasound transducer, excitation across the entire range of audio frequencies was obtained. Since the beam was focused on the reed, ultrasound stimulated excitation eliminated background effects observed during mechanical shaker excitation, such as vibrations of clamps and supports. The results obtained using single, dual and confocal ultrasound transducers in AM and two-beam modes, along with results obtained using a mechanical shaker and audio excitation using a speaker are discussed.
本研究的目标是以非接触方式激发并测量簧风琴管簧片的振动模式。为了进行超声激发，一对超声束之间的音频差频产生了诱导振动的辐射力。用扫描激光测振仪测量由此产生的振动偏转形状。使用该技术可以在空气中研究任何相对较小物体的共振。对于一个36毫米×6毫米的黄铜簧片，在145赫兹的基频下，可以施加超过5微米的位移和4毫米/秒的速度。使用同一个超声换能器，可以在整个音频范围内获得激发。由于光束聚焦在簧片上，超声激发消除了在机械振动台激发过程中观察到的背景效应，如夹具和支架的振动。讨论了在调幅和双光束模式下使用单、双和共焦超声换能器获得的结果，以及使用机械振动台和扬声器进行音频激发获得的结果。
