As Professor of Vocal Physiology in the University of Boston, he was
engaged in training teachers in the art of instructing deaf mutes how to
speak, and experimented with the Leon Scott phonautograph in recording
the vibrations of speech. This apparatus consists essentially of a thin
membrane vibrated by the voice and carrying a light stylus, which traces
an undulatory line on a plate of smoked glass. The line is a graphic
representation of the vibrations of the membrane and the waves of sound
in the air.
On the suggestion of Dr. Clarence J. Blake, an eminent Boston aurist,
Professor Bell abandoned the phonautograph for the human ear, which it
resembled; and, having removed the stapes bone, moistened the drum with
glycerine and water, attached a stylus of hay to the nicus or anvil, and
obtained a beautiful series of curves in imitation of the vocal sounds.
The disproportion between the slight mass of the drum and the bones it
actuated, is said to have suggested to him the employment of
goldbeater's skin as membrane in his speaking telephone. Be this as it
may, he devised a receiver, consisting of a stretched diaphragm or drum
of this material having an armature of magnetised iron attached to its
middle, and free to vibrate in front of the pole of an electro-magnet in
circuit with the line.
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