Physical Acoustics Summer School

PASS at the Summit: Report of the 2014
Physical Acoustics Summer School

Joseph R. Gladden and George Atkins

National Center for Physical Acoustics, University of Mississippi, Oxford, MS

Kent L. Gee and Tracianne B. Neilsen

Department of Physics and Astronomy, Brigham Young University, Provo, UT

DOHM-wah-wah-wah…. The unique tones of a large Balinese gamelan gong was a familiar sound during the 2014 installment of the Physical Acoustics Summer School (PASS), which was held 28 May – 02 June 2014 at Daniels Summit Lodge.  The summit, nestled in the Wasatch mountains at a rarified altitude of 8000 ft and located about one hour from Provo, Utah, was a scenic backdrop for elevated discussions of advanced topics in physical acoustics.  The gong, which relies on nonlinear coupling between vibrational modes to produce its unique sound, served as a Pavlovian call to order at the start of lectures and discussions.

Physical Acoustics Summer Schools have been held biennially since 1992, but 2014 marks the first time it has been held in Utah.  The week-long schools were developed at the encouragement of Logan Hargrove, retired scientific program officer at the U.S. Office Naval Research, and who has been at every PASS since its inception.   The school’s purpose is to bring graduate students, distinguished lecturers, and professionally mature discussion leaders together to discuss a variety of subjects in physical acoustics.  This gives students an opportunity to learn from experts who will discuss topics not often offered at universities due to the relatively small demand at any one institution.  PASS 2014 was dedicated to the memory of Dick Stern, former editor of Acoustics Today and long-time champion of PASS.  The school was sponsored by the Acoustical Society of America, National Center for Physical Acoustics at the University of Mississippi, and the Applied Research Laboratories at the University of Texas at Austin.

During the past two decades, almost 400 graduate students have attended PASS.  Students have come from 36 different U.S. universities and eight different countries.  The PASS class of 2014 was comprised of 31 students from eight U.S. and three international universities – Brigham Young University, Colorado School of Mines, University of Illinois, University of Mississippi, Nanyang Technical University (Singapore), University of Nebraska-Lincoln, University of Oxford (U.K.), Pennsylvania State University, University of Texas at Austin, University of Twente (Netherlands), and Washington State University.  Their fields of study were diverse, spanning topics associated with multiple ASA technical committees – including architectural acoustics, biomedical acoustics, noise, physical acoustics, structural acoustics, and underwater acoustics.   The diversity of backgrounds and areas of study led to fascinating interactions during mealtimes and social hours!

The heart of PASS is the three-hour lectures given by experts within their respective fields and evening discussions.  The lecturers and topics are listed in Table 1.  Greg Swift gave an engaging presentation on thermoacoustics where the students learned operating principles of bottle rockets, Knipp’s singing tubes, and thermoacoustic engines.  Preston Wilson explained the foundational principles of bubble dynamics and their impact on a variety of applications.  This topic was foundational to parts of subsequent lectures by Mark Hamilton, who spoke on principles, modeling, and experiments in nonlinear acoustics, and Mike Averkiou, who discussed different types and applications of ultrasonic imaging and therapy.  A lecture by Tom Gabrielson helped attendees understand the deleterious and often subtle effects of transducer and measurement noise in data.  His talk was complemented by an evening discussion of various time-series analysis techniques led by Garth Frazier of the National Center for Physical Acoustics.   Two lectures on physical acoustics in solid media rounded out the PASS – Veerle Keppens spoke on the principles of solid state physics and the use of resonant ultrasound spectroscopy and Jay Maynard explored types of wave propagation and connections to quantum mechanics and crystalline structures.

A traditional highlight of PASS has been a demonstration show that emphasizes in-depth discussion of principles, particularly those not encountered in the typical student curriculum.  At PASS 2014, an entire day was devoted to exploring demonstrations.  In the morning, Steve Garrett from Penn State led the students in building their own thermoacoustic lasers and Scott Sommerfeldt and Yin Cao from Brigham Young University discussed and demonstrated global active noise control.  In the afternoon, attendees were treated to a show that included demystifying the Balinese gong, demonstrating chaos from a cymbal, simjet noise crackle, organ-pipe mode locking, and visualization of vibrational modes.  The show culminated with a real outdoor experiment and analysis of a nonlinear sound source – large acetylene-oxygen balloon explosions that produced shock waves with 170 dB levels.

We would be remiss if we didn’t mention that with all the learning came some opportunities to play.  In addition to cavitation-induced bottle breaking during evening social hours, attendees took time off to hike two miles to visit a 200 ft waterfall in Provo Canyon or to visit the Olympic Village, art galleries and museums in Park City.  These experiences help round out the unique mission of PASS – to not only transfer and build a broad knowledgebase, but to create relationships that last well beyond than the week’s lectures.   One-time students have become discussion leaders, lecturers, and organizers and PASS participants have created groups on Facebook and connected on Linkedin, allowing for sharing of ideas, collaboration, and career opportunities.   We are grateful for ASA’s support of PASS and are already looking forward to 2016!