Gustavus Adolphus College Acoustics Lab

Thomas Huber

HuberPhysics YouTube Channel



Optical measurements of acoustic fields using refracto-vibrometry

Talk for Acoustical Society of America Meeting
December 8, 2020




Ultrasonic Wave Propagation in Acrylic Samples Measured with Refracto-Vibrometry




Selected Recent Publications

Boston ASA2017 Presentation: Spatial Distribution of Acoustic Radiation Force
Boston ASA2017 Presentation: Refracto-Vibrometry Visualization of Ultrasonic Waves in Calcaneus Heel Bones

Poster for Summer 2014 American Association of Physics Teachers Meeting

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

Visualization of Sound Fields: Reflection of Sound Wave in Closed Tube
The goal of this experiment was to measure a sound pulse emitted from a speaker as it travels through a transparent acrylic tube and reflects off the ends. Note that the waveform is not inverted after its reflection from the closed end of the tube.
This material is based upon work supported by the National Science Foundation under Grant Numbers 0959858, 0963491, 1300591 and 1635456. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation (NSF)