The Von Bekesy – Gold Controversy

gt While both of these renown American scientists were foreign born, they both emigrated to the US furthering their already stellar scientific careers.   Georg von Bekesy (1899-1972), a Hungarian citizen, he had moved to the United States in 1947 after working in various European laboratories and found himself at the Harvard University in the Psycho-Acoustic Laboratory. At the time, the labs at Harvard were the “seat” of hearing research worldwide, led by the likes of S.S. Stevens, colleagues such as Robert Galambos and  collaborating with the Electroacoustic Laboratory, headed by Leo Baranek.

 In the 1961, it would seem that the cochlear mechanics were all figured out…..After all, von Bekesy had won the Nobel Prize in Physics and Medicine for developing agt3 method for dissecting the inner ear of human cadavers while leaving the cochlea partly intac.  This allowed him to use strobe photography and silver flakes as a marker to observe that the basilar membrane moves like a surface wave (the traveling wave) when stimulated by sound.  He found that due to the structure of the cochlea and the basilar membrane, different frequencies of sound cause the maximum amplitudes of the waves to occur at different places on the basilar membrane along the coil of the cochlea. High frequencies cause more vibration at the base of the cochlea while low frequencies create more vibration at the apex.  Von Bekesy concluded that his gt6observations showed how different sound wave frequencies are locally dispersed before exciting different nerve fibers that lead from the cochlea to the brain. He theorized that the placement of each sensory cell (hair cell) along the coil of the cochlea corresponds to a specific frequency of sound (the so-called tonotopy).  Békésy later developed a mechanical model of the cochlea, which confirmed the concept of frequency dispersion by the basilar membrane in the mammalian cochlea. 

Austrian born, Thomas Gold (1920-2004) became well known for his work in biophysics, astronomy, aerospace engineering and geophysics. His distinguished career was at Cambridge, Harvard and Cornell.  Although Gold won a prize fellowship from Trinity College at Cambridgegt3 for his thesis that the ear operates by “regeneration”, an  electromechanical action that occurs when electrical energy is used to counteract the effects of damping. Although Gold won the prize fellowship for his thesis on regeneration and obtained a junior lectureship at the Cavendish Laboratory, his theory was widely ignored by ear specialists and physiologists, such as von Békésy, who did not believe the cochlea operated under a feedback system.  Gold’s work, done in collaboration with his doctoral advisor, RJ Pumphrey (Gold and Pumphrey 1948), was the first to consider that the ear cannot simply act passively, as was theorized by both Helmholtz and von Békésy, but that it must be an activegt5 detector. Gold had been a physicist who conducted wartime work on radar, and he brought his signal-processing knowledge to bear on how the cochlea works. He knew that, to preserve signal-to-noise ratio, a signal had to be amplified before the detector, and that ‘surely nature can’t be as stupid as to go and put a nerve fibre—that is a detector—right at the front end of the sensitivity of the system’. He, therefore, proposed that the ear operated like a regenerative receiver, much like some radio receivers of the time that used positive feedback to amplify a signal before itgt2 was detected. Regenerative receivers were simple—one could be built with a single vacuum tube—and they provided high sensitivity and narrow bandwidth. A drawback, however, was that, if provoked, the circuit could ‘take off’, producing an unwanted whistle.

In his research von Bekesy’s first theory, sympathetic resonance, there is an advantage of allowing vanishingly small energies to build up, cycle by cycle, into an appreciable motion—like boosting (or “pumping”) a child on a swing. The second, travelling wave, has the weight of von Békésy’s extensive experiments behind it. At the same time, one of the drawbacks of the travelling wave theory is the difficulty of accounting for the ear’s exquisite fine tuning: trained musicians can easily detect tuning differences of less than 0.2%. Even von Békésy himself notes, on page 404 of his classic book, Experiments in Hearing, that ‘the resonance theory of hearing (as postulated by Gold, 1948) is probably the most elegant of all theories of hearing’.

At the time, however, these were the two theories of cochlear mechanics……..In the figure to the right,  many hearing scientists believed as did von Bekesy in a passive model of the cochlea, shown in figure A. Gold’s  alternative view, a resonance theory, suggested that independent elements on the cochlear partition can vibrate side to side in sympathy withgt4 incoming sound.  It remains open whether the resonant elements on the cochlear partition are set off by a traveling wave (giving a hybrid picture of cochlear mechanics) or directly by sound pressure in the liquid (resonance alone).  

Gold connected this with the perception of ringing in the ear (tinnitus), and daringly suggested that if a microphone were put next to the ear, a corresponding sound might be picked up. He gt5experimented, placing a microphone in his ear after inducing temporary tinnitus with overly loud sound. The technology wasn’t up to the job—in 1948 microphones weren’t sensitive enough—and the experiment, sadly, failed. In the 1970s, researchers discovered that Gold’s hypothesis had been correct – the ear contained microscopic hair cells that operated on a feedback mechanism to generate resonance. New technological capability of microphones led to the discovery of the “Kemp Echoes” or Otoacoustic Emissions. Obviously, von Bekesy’s assumption that the cochlea was a passive system was not correct.

Dr. Jay Hall , summed up the von Bekesy-Gold Controversy very well a few years ago in his book In retrospect, it is easy to conclude that, due to his fondness for conducting investigations in cadavers, the brilliant von Bekesy would never have discovered active processes within the cochlea, nor even imagined the possibility of otoacoustic emissions.  To be blunt, dead men (and women) don’t have OAEs.”

 

About Robert Traynor

Robert M. Traynor is a board certified audiologist with 45 years of clinical practice in audiology. He is a hearing industry consultant, trainer, professor, conference speaker, practice manager, and author. He has 45 years experience teaching courses and training clinicians within the field of audiology with specific emphasis in hearing and tinnitus rehabilitation. Currently, he is an adjunct professor in various university audiology programs.