Noncontact Modal Excitation of a Classical Guitar Using Ultrasound Radiation Force
Previous studies have demonstrated that it is possible to use the ultrasound radiation force in air for modal excitation of objects ranging in size from microcantilevers that are a few hundred microns in length to hard drive suspensions and other cantilevers a few centimeters long. The current study demonstrates that the ultrasound radiation force excitation technique can also be used for modal excitation of significantly larger objects, in this case an acoustic guitar. It was demonstrated that the noncontact combination of ultrasound radiation force excitation and a scanning vibrometer allowed measurements of both the frequency response and operating deflection shapes of a Cordoba 45R classical guitar in the range from 70 to 800 Hz. The resonance frequencies and deflection shapes are similar to those measured using a conventional mechanical shaker. By using a pair of ultrasound transducers and adjusting their relative phase difference, it was possible to selectively enhance or suppress different resonances. This is a substantial extension over previous studies because the guitar is several orders of magnitude larger than devices used previously.
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Document Type: Research Article
Affiliations: Physics Department, Gustavus Adolphus College, Saint Peter 56082, MN, USA
Publication date: 01 July 2013