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THE EDISON WAY
From his early youth, Edison was hard of hearng. Perhaps thatís why he devoted much of his
time to the study of sound. He knew that the vibrations of the human eardrum, which is really a
diaphragm, were communicated to the inner ear
and that this caused the sensation of sound.
His experiments with megaphones, vibrating diaphragms, and the telephone transmitter were all stepping stones to his invention of the phonograph in 1877.
Edisonís phonograph reproduced sound as follows: a pick-up stylus tracking the grooves of a recording (Edison used tin foil wrapped around a cylinder) vibrated in accordance with the sound impressions in those grooves. Being attached to a diaphragm, the stylus caused the diaphragm to vibrate at the same rate. The diaphragm then emitted sound waves, which were made audible by a mechanical horn. Letís see if we can reproduce sound the way Edison did.
A Phonograph Pick-Up
|Materials: Frozen juice can. Aluminum foil. Small cork. Sewing needle. Phonograph record ( don't use a good one). Smooth cardboard. Ballpoint cartridge.|