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Academy of Sciences in 1983. Although none of the discov- eries made in Izzy’s lab were recognized by a Nobel Prize in Physics, the 2016 prize, awarded to Kosterlitz, Thouless, and Haldane, recognized Izzy’s contribution that was made through acoustic measurements near absolute zero and established the universality of the two-dimensional topo- logical phase transition during the superfluid transition in atomically thin films of superfluid helium (He II).
This article reviews some of Izzy’s landmark contributions to both classical acoustics and to the understanding of the behavior of superconductors and quantum fluids, but more importantly, it will attempt to document the career of a great physicist during a period of unprecedented change as phys- ics transitioned from the late 19th century triumphs of clas- sical analysis, epitomized by Lord Rayleigh’s Theory of Sound (Strutt, 1896) to ongoing attempts to unravel the implica- tions introduced by the emergence of quantum mechanics.
“Talkies” Were His Path to Acoustics
Born in New York City, Izzy moved with his family to Los An- geles at an early age. He became interested in physics while he was an undergraduate student at UC, Berkeley during the de- pression. To cover his living expenses, he worked as a lab as- sistant to a physics PhD student, about whom he commented, “The guy was working on his PhD. I was appalled that this guy, who I really had such a high opinion of, couldn’t find a job. He did get a job with the USA group that studied weather where he translated French books on the weather into Eng- lish. That’s all he could find. I decided right then that some- how I’m going to find a way to get a decent job. I was talking to Moshe Kadish [a friend from high school] about it, and he said he heard that down in Los Angeles, people were making money by [improving the audio quality of] movies that have voices on them. They called them ‘talkies’.”
During a trip to Los Angeles, Izzy wrangled an appointment to speak with Vern Knudsen, a physics professor at UC, Los Angeles (UCLA) and consultant to the film industry in Hol- lywood. Knudsen was designing “sound stages” and reduc- ing the noise made by cameras at that time. Izzy believed he did not impress Knudsen “because I didn’t have such a hot record. I had to go back to Berkeley for another semester. I did that, and then I got straight As.” Ultimately, he trans- ferred from UC, Berkeley to UCLA where he received his BS (1938) and MS (1940) in physics followed by a PhD thesis under Knudsen’s supervision (1944).
The Classical Era
After wartime research at Duke as a postdoc, Izzy took a junior faculty position at Pennsylvania State College (now University) in 1945 and then returned to UCLA in 1948, where he served as a professor of physics for 39 years, pro- ducing 32 PhD students and hosting postdoctoral fellows and visiting international scholars.
Before his return to UCLA, Izzy had already significantly advanced our understanding of classical acoustics in sev- eral areas. These included atmospheric sound propagation through turbulence and along a porous boundary. He also demonstrated the application of the reciprocity technique for free-field calibration of condenser microphones to fre- quencies as high as 100 kHz and studied the attenuation of sound in soil, which earned him the moniker “Dr. Mudnick.”
Also notable were studies of nonlinear distortion and the effects of high-amplitude sound that were enabled, in part, by the development with Clayton Allen1 of a special type of siren that was the most powerful man-made sound source at the time. That source was shown to produce “whiter whites” through ultrasonic laundry.
Izzy was asked by the US Navy to measure the sound levels on the flight decks of aircraft carriers. The Navy was worried that the introduction of jet aircraft could cause significant hearing damage. Izzy’s measurements confirmed this hypothesis, but the sailors were unwilling to wear hearing protectors because they felt it conflicted with their macho self-image. Apparently, Izzy was as good a psychologist as he was a physicist. He wrote an article for the ship’s newspaper pointing out that in addi- tion to hearing loss, high-intensity sound exposure was also suspected to cause impotence. The next day, it was observed that all of the crew on the flight deck were wearing hearing protectors (presumably over their ears).
At UCLA, his investigations of high-amplitude sound con- tinued with studies of acoustically induced streaming (with Herman Medwin), attenuation of repeated shock waves, and harmonic distortion produced in the throats of horn- coupled loudspeakers. Izzy encountered R. W. Leonard, who was also on UCLA’s physics faculty and was interested in the attenuation of sound due to relaxation processes. “He [Bob Leonard] had a real talent for building experiments just the
1 Readers who want to go beyond this biography of Dr. Rudnick and read the original research papers from his lab can find all of the citations, by the investigators mentioned in the article, at http://acousticstoday.org/rudnick- references/. In addition, the actual articles can be found on a CD of Dr. Rudnick’s Collected Works (Maynard and Garrett, 2011).
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