Alexander Graham Bell’s Dead Ear Phonautograph, the Invention that Inspired the Telephone

In 1874, Alexander Graham Bell created a phonautograph, an early device for recording sound, using the ear and part of the skull of a dead man. He attached a recording stylus to the eardrum, which, when vibrated by sound, inscribed lines on a smoked-glass plate.

When Bell spoke into the dead man’s ear, the stylus etched the vibrations onto the glass.

A mouthpiece, or “speaking trumpet,” funneled the sound of Bell’s voice to an eardrum from a cadaver. The sound waves caused the inner ear bones to vibrate. A piece of straw – attached at one end to the bones – traced the pattern of the vibrations onto a charcoal-coated glass plate moving under the straw’s tip.

The straw’s tracings recorded each sound as a series of waves. As Bell’s voice changed pitch, the speed of vibrations changed and so did the pattern’s shape.

As a teacher in a Boston school for the deaf, Bell thought such a device might allow his students to learn to speak a language they were unable to hear by recognizing the visual representations inscribed in the glass.

The students could record their own speech, and improve by comparing the tracings.

“The teachers in the school for the deaf had been trying to teach the children to speak, and had met with good success,” Bell Wrote. “But the teachers made a claim that seemed to me to be ridiculous. They claimed not only that deaf children could be taught to speak, but that after they had been taught to speak, they could come to understand speech by looking at the mouth of the speaker. I did not dare to say no, but I did not believe it, and out of my skepticism about lip reading grew the telephone.”

Sound etchings made by Alexander Graham Bell’s ear phonautograph

“I went to a distinguished aurist of Boston, and told him I wanted to make a phonautograph, modeling it after the ear,” Bell wrote. “He replied, ‘Why don’t you use a human ear itself, taken from a dead man, as a phonautograph?’ That was quite a new idea, and I said, ‘I shall be very glad to do that, but where can I get a dead man’s ear?’ ‘Oh,’ he said, ‘I will get it for you,’

The aurist, Dr. Clarence J. Blake, procured an ear for Bell, and as soon as summer vacation began, Bell got to work.

“I took the human ear with me in order to get tracings. I moistened the membrane with glycerine and water, attached a piece of hay to one of the little bones, and rigged up an apparatus for dragging a piece of smoked glass underneath. Through a speaking trumpet I spoke into that dead man’s ear, and obtained beautiful tracings of the vibrations upon smoked glass.”

The success of the phonautograph got Bell thinking.

He surmised that if you could use sound to get an electrical current to vibrate like the stylus, then you could send speech as far and fast as electricity could travel.

“As I was holding the human ear in my hand, it struck me,” Bell said, “that the bones of that human ear were very massive compared to the membrane. The membrane was like a little piece of tissue paper, hardly the size of a finger nail, and the bones that were moved by the little membrane were really very heavy. It suddenly occurred to me, that if such a small membrane as that would move bones so massive in comparison, why would not a larger membrane move my piece of iron? At once the idea of a membrane speaking telephone became complete in my mind. All I had to do was to attach a steel reed, not tuned to any definite pitch, to the center of a stretched membrane, just as in the phonautograph, so that it would vibrate in front of an electromagnet, and put another at the end of a telegraph wire, and we would have . . . a speaking telephone.”

Bell’s human ear apparatus as illustrated in The Telephone, the Microphone and the Phonograph, 1879

So we have a dead man’s ear to thank for the phones we carry with us today.