Questions and answers with Eric J. Heller
DOI: 10.1063/PT.4.2461
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Eric (Rick) Heller is the Abbott and James Lawrence Professor of Chemistry and professor of physics at Harvard University, where he received his PhD in chemical physics in 1973. He has held faculty positions at UCLA and the University of Washington and a scientific staff position at Los Alamos National Laboratory in New Mexico.
Heller’s research focuses on few-body quantum mechanics, spectroscopy, scattering theory, nanophysics, and condensed-matter physics. He also produces computer-generated prints based on his research. His art has been featured in private and public collections, in traveling exhibits, and on his website .
While teaching The Physics of Music and Sound, an acoustics course aimed at Harvard nonscience majors, Heller conceived of the idea for his recently published text, Why You Hear What You Hear: An Experiential Approach to Sound, Music, and Psychoacoustics (Princeton University Press, 2013). Its accompanying website hosts such supplementary material as animations, instructional videos, and sound. Physics Today recently caught up with him to discuss the book.
PT: By size alone, your 600-page text seems quite comprehensive; what motivated it?
HELLER: I became quite dissatisfied with existing [acoustics] textbooks. Some were delightful but small and idiosyncratic, others wonderful but ancient. Modern full-blown texts had poor graphics and took no advantage of personal computers or of freely available, user-friendly sound generation and analysis software.
I began to discover some fairy tales that were being propagated. Every field has its simple mnemonics for student learning, but some were going too far and missing opportunities. For example, … it’s just plain misleading to treat the vocal tract as a subtractive filter, omitting to mention the resonances that enhance the power of the vocal folds far above what it would be without the vocal tract. Of course, all good professionals know about resonance, but is it so abstruse that we must hide it from students, musicians, vocalists, architects? No. It’s a shame to leave the impression that an opera singer can only get above an orchestra by straining, instead of [by] shaping a part of the vocal tract to create a resonance, a singer’s formant.
In the end, as I started to research [the book], I fell in love with acoustics. I sensed a unifying approach to teaching acoustics that I wanted develop and then to share. Everyone I met in the field was helpful, open, and friendly—this was a very important factor.
PT: How will physics majors benefit from this book? How will nonphysicists—musicians, speech therapists, architects—benefit?
HELLER: Why You Hear What You Hear is presented at an elementary mathematical level, but conceptually it’s a high-level book. This is made possible by the 400 figures, many applets, and sound files, which build intuition without higher mathematics. The website is full of graphics, applets, and interactive examples. For musicians, sound engineers, speech therapists, and architects, I think a gut level, intuitive understanding of one’s medium is empowering and inspires innovation. For physics majors, gaining an intuition for wave behavior helps in a huge range of fields, and acoustics is the most accessible place to gain that intuition. I wish I had understood many of the things in this book much earlier in my career.
PT: You’ve put a great deal of content and many exercises on the website. What are the advantages and disadvantages of doing that?
HELLER: All the major concepts are in the book proper. But the attempt to impart high-level intuition depends on interactive, cross-platform applications and examples. There are some absolutely wonderful web-based acoustics tools out there. As we all know, such things change, go out of date, and new ones become available. It simply would not do to [print URLs that] would be obsolete in 12 months. The website allows me to keep things current and, more than that, to keep improving the content. It also makes accessible animations, instructional videos, and sound—[which] cannot be put on paper. I have made a considerable effort to collect the best resources available in one central location, in a way that reinforces the content of each chapter (for an example, see here ).
The disadvantage is I’m never done with the book!
PT: You have unusually broad interests and expertise. What in particular fascinates you about acoustics?
HELLER: I love wave phenomena of all kinds. Acoustics makes wave behavior palpable, more so than quantum mechanics or electrodynamics. Acoustics has taught me new things [that] somehow had eluded me in spite of my lifelong fascination with waves.
Years ago, I tried to become a professional trumpet player. My talent, in retrospect, was not nearly sufficient. More recently, I was disappointed to discover that knowing quantum mechanics didn’t bring me very close to understanding how a trumpet works. It truly fascinated me to understand the instrument from the acoustician’s point of view, and then I was hooked on acoustics.
PT: Can you provide an example or two of your visual and acoustic work and discuss how they demonstrate general physics principles?
HELLER: Here’s a case in point: How do marimba resonators work? What you’ll normally read is that the marimba tube is tuned to the vibrating wooden key lying just above it, and resonators make things louder when they are driven on resonance. This is where almost all sources stop, but it is already totally misleading. A baffled, monopole-source loudspeaker, for example, is not any more enhanced by a tuned resonator nearby than [by] a blank wall. However a dipole or quadrupole source, such as an oscillating wooden marimba key or a tuning fork, is largely self-canceling in the far field. If a resonator is placed very nearby and manages to capture a part of the intense near field, it can reradiate the energy with a shifted phase and from a slightly different location. The self-cancellation is foiled and the result is much louder sound. This fact is useful in atomic physics, antennae performance, and a host of other applications. This “near-field capture and release” is illustrated by figures in the book: screen shots of simulations [produced with] a freely available Java wave applet, written by Paul Falstad and modified by the Instructional Computing Group at Harvard (and available here ).
PT: What books are you reading now?
HELLER: I am reading The Rise and Fall of the Third Reich (by William Shirer; 50th anniversary edition; Simon and Schuster, 2011). Surely one of the most frightening books I have ever read.
