Sonotone Model 400 Carbon Hearing Aid
The Sonotone Model 400 carbon hearing aid was
manufactured in 1932 by Sonotone International, Inc. of New York.
This hearing aid came with a bone conduction transducer rather than a
receiver.
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Front view of the Sonotone Model 400 carbon hearing aid double
microphone showing the pattern of each of the microphone grills—12 holes in the outer ring, 6 holes in the middle ring and
one hole in the center. The double microphone measured 5⅛" wide x
2˝" high x ⅝" thick, and weighed 4.6 oz. Note the large triangle with
the big stylized "S" in the center.
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Rear view of the Sonotone Model 400 carbon hearing aid double microphone.
Below the pocket
clip (top center) very faintly are the words "Sonotone Corp, New York" and just below
the center, the serial number S-90505.
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Top side view of the Sonotone Model 400 carbon hearing aid double
microphone showing the three-pin body plug and socket. Note that the
socket is recessed into the body, not flush with the surface as was the
case with later hearing aids.
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Side view of the above plug showing the name "Sonotone" and below that,
"New York".
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Bottom side view of the Sonotone Model 400 carbon hearing aid double
microphone showing the on-off/volume control slider (shown in the off
position), and the "foot" swung out so it could stand on a table. |
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Side view of the Sonotone Model 400 carbon hearing aid carbon amplifier
showing the name "Sonotone", "New York" and "US. Patent 1,939,627".
The two pins on the bottom of the carbon amplifier plugged directly into a battery such as
the
Sonotone Model X42 3-volt battery.
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End view of the Sonotone Model 400 carbon hearing aid carbon amplifier
showing the 3-pin plug and socket. This plug is slightly smaller than
the body plug so you can't accidentally interchange them.
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View of the Sonotone Model 400 carbon hearing aid bone conductor
transducer showing the end of the transducer with the cable plugs and
transducer jacks. The plugs are different sizes so can only plug in the
"right" way.
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View of the back of the Sonotone Model 400 carbon hearing aid bone conductor
transducer showing the pattern on its back.
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End view of the Sonotone Model 400 carbon hearing aid bone conductor
transducer showing the stylized Sonotone "S".
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View of the Sonotone Model 400 carbon hearing aid bone conductor
transducer and headband.
The headband held the transducer tightly to the mastoid bone behind
the ear for efficient transfer of the sound vibrations to the skull.
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