I Can Hear You Whisper by Lydia Denworth Page B

ear) attached to a headband for duPont to wear. Hidden under the table was a desk-size set of amplifiers, transformers, and condensers. By using two receivers instead of one, duPont was able to tell where the speaker was. “And that,” said Fletcher, “wasthe first hearing aid Bell Labs ever made.” Later,Fletcher made hearing aids for Thomas Edison as well, though Edison later complained that his hearing aids had revealed to him that speakers at the public events he attended said little of interest.
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    Fletcher wasn’t the only one whose work was inspired by the telephone. In the 1920s, just as the Bell Labs team was investigating the properties of speech and hearing, Hungarian scientist Georg von Békésy began zeroing in on just one component of that chain: the inner ear. After completing his PhD in physics in 1923 at the University of Budapest, Békésy took a job at the Telephone System Laboratory at the Hungarian Post Office, which maintained the country’s telephone, telegraph, and radio lines. “After World War I, [it was] the only place in Hungary that had some scientific instruments left and was willing to let me use them,” he said later. His job was to determine whether making changes in the telephones themselves or in the cables led to greater improvements in telephone quality. His engineering colleagues wanted to know “which improvements the ear would appreciate.” At first, Békésy turned to library books for answers. But he soon realized that while a lot was known about the anatomy of the ear, very little was understood about its physiology, how it actually worked. He began studying the function of the inner ear, and the subject became his life’s work.
    Békésy wanted to see the cochlea in action, and I do mean “see.” He collected an assembly line of temporal bones from cadavers at a nearby hospital and kept them in rotation on his workbench. First, he made models of the cochlea based on his samples, then he began to do experiments with the human cochlea. Using a microscope that he designed himself to send strobes of multicolored light onto the inner ear, he watched the basilar membrane, the cellophane-like ribbon that runs the length of the cochlea, as it responded to sound. The setup he rigged allowed him to see a sound wave ripple from one end of the basilar membrane to the other. He also identified critical properties of the membrane, that it was stiff at one end and more flexible at the other. Although the idea that different places on the basilar membrane responded to different frequencies had already been posited, Békésy was the first to see that response with his own eyes: The displacement of one part of the membrane was greater than the rest, depending on the frequency of the tone. His discovery was calledBékésy’s traveling wave.
    After World War II, not wanting to live in what had become Communist Hungary, Békésy continued his work first at the Karolinska Institute in Sweden and then at Harvard. A loner by nature, he never taught a student or collaborated with anyone. Nevertheless, he was awarded the Nobel Prize in Physiology or Medicine in 1961 for his work on “the physical mechanism of stimulation within the cochlea.” Nobel Prize or no, we know today that there are at least two fundamental problems with Békésy’s work. One is that his subjects were dead. The auditory system is a living thing and responds more subtly when alive than dead. Secondly, in order to get any response from the cochlea of a cadaver, he had to generate noise that was loud enough (134 dB) to wake the dead, so to speak. As a result, the broad response Békésy saw didn’t accurately reflect the finesse of the basilar membrane. Despite its limitations, Békésy’s traveling wave represented an important advance. In a recent appreciation of his work, Peter Dallos and