I Can Hear You Whisper by Lydia Denworth Page A

to make speech intelligible to the deaf.
    They did see the potential to help in other ways immediately. With his new arsenal of oscillators, amplifiers, and attenuators, Harvey Fletcher could for the first time accurately measure hearing, because he could now produce a known frequency and intensity of tone. He patentedthe audiometer that was the forerunner of the machines used in Alex’s hearing test. His group alsocreated the decibel to measure the intensity of sound as perceived by humans, and they established the range of normal hearing as20 to 20,000 Hz. The range of speech from awhisper to a yell proved to span about sixty decibels. The new audiometer could measure noise as well, which allowed the editors of the August 1926 issue of
Popular Science Monthly
to note that a Bell Labs device had identified the corner ofThirty-Fourth Street and Sixth Avenue as the noisiest place in New York City. A decade later, Bell scientists capitalized on demonstrations at the1939 World’s Fair and measured the hearing of enough curious fairgoers that they were able to show just how much hearing degrades from the teenage years into late middle age.
    Fletcher’s newfound abilities and equipment brought him some interesting visitors. When American industrialist and philanthropistAlfred I. duPont couldn’t hear what was being said at his own board meetings, he turned to Bell Labs for help. After a childhood swimming accident in the Brandywine River, duPont’s hearing had gotten progressively worse, and he was almost entirely deaf as an adult. DuPont told Fletcher that his ability to hear fluctuated. It improved after X-ray beam treatment from a doctor he was seeing, then worsened again. Skeptical, Fletcher asked to accompany duPont on his next visit to the doctor. Beforehand, Fletcher measured duPont’s hearing himself and created a picture of his considerable hearing loss using what he called an “embryo audiometer.”According to Fletcher, the doctor treating duPont had a very different technique.
    There was a path along the floor . . . about 20 feet long. Mr. Dupont was asked to stand at one end of this. The doctor stood at the other end and said in a very weak voice, “Can you hear now?” Mr. Dupont shook his head. [The doctor] kept coming closer and asking the same question in the same weak voice until he came to about two feet from his ear, where [Mr. Dupont] said he could hear. His hearing level was found to be two feet.
    Mr. Dupont then was asked to stand four or five feet in front of an X-ray tube with his ear facing the tube. The X-ray was turned on two or three times. He then turned his other ear toward the tube and had a similar treatment. He then stood in the 20 foot path and another hearing test was made. But this time as he started to walk toward Mr. Dupont [the doctor] shouted in a very loud voice: “Do you hear me now?” As the doctor reached the 10 or 15 foot mark, Mr. Dupont’s eyes twinkled and he said he could hear.
    I could hardly keep from laughing. . . .
    When they returned to the laboratory, Fletcher measured duPont’s hearing again and found it unchanged. “After that,” noted Fletcher, “Mr. Dupont never paid a visit to this doctor.”
    Fletcher and duPont then turned to the problem of the board meetings. The invention of the telephone had led to the first electronic hearing aids by making it possible to manipulate attributes of sound like loudness and frequency as well as to measure distortion. (Likewise, the invention of the transistor at Bell Labs in the 1950s would revolutionize hearing aid technology by making the devices smaller and more powerful.) One early electronic hearing aid apparently consisted of a battery attached to a telephone receiver. For duPont to hear all the participants in a meeting, Fletcher set up a system with two microphones in the center of the boardroom table and two telephone receivers (one for each