Guitar Research: Ultrasound Excitation of Mode Shapes of a Guitar The goal of this experiment was to demonstrate that ultrasound radiation force excitation can be used as a noncontact
method for modal excitation as an alternative to a standard mechanical shaker. While this has been demonstrated for
small objects, this demonstrates that modal excitation is possible for objects as large as a classical guitar.
By using both the ultrasound radiation force excitation and scanning vibrometer, it is possible to perform completely
noncontact modal analysis!
Guitar String Vibration An acoustic guitar was excited by a 4 millisecond long
"tap" from a mechanical shaker that struck the D-string to simulate a
single string being plucked. The velocity of the string was measured using a Polytec PSV-400 scanning laser Doppler vibrometer. For this measurement, there was a capo on the 6th fret, just out of the field of view of the photograph
and vibrometer measurement. The video shows the first few reflections as the wave bounces back and forth along the string.
Reed Organ Pipe Research Airflow was repeatadly initiated for an organ reed pipe (Oboe at 263 Hz). The velocity of the
reed was measured using a Polytec PSV-400 scanning laser Doppler vibrometer.
The video shows the velocity profile as the reed begins to oscillate and reaches its steady state.
The peak acceleration towards the end of the reed exceeds 40 km/s2, or 4000 g's, when it impacts the
shallot and snaps from negative to positive
This material is based upon work supported by the National Science Foundation under
Grant Numbers 0959858 and 0963491.
Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s)
and do not necessarily reflect the views of the National Science Foundation (NSF)