Noncontact modal analysis of a pipe organ reed using airborne ultrasound stimulated vibrometry

Thomas M. Huber, Mostafa Fatemi, Randy Kinnick, James Greenleaf

Research output: Contribution to journalArticle

25 Scopus citations

Abstract

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 μm 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.

Original languageEnglish (US)
Pages (from-to)2476-2482
Number of pages7
JournalJournal of the Acoustical Society of America
Volume119
Issue number4
DOIs
StatePublished - Apr 1 2006

ASJC Scopus subject areas

  • Arts and Humanities (miscellaneous)
  • Acoustics and Ultrasonics

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