Sonotone Model 451 Carbon Hearing Aid The Sonotone Model 451 carbon hearing aid was manufactured in 1937 by Sonotone International, Inc. of New York. This Sonotone microphone was made out of faux tortoiseshell and was a beautiful translucent reddish color, especially with the light shining through it. This hearing aid without the battery weighed 7.7 oz (218 g). | | Click picture for larger view | | | | |
Front view of the Sonotone Model 451 carbon hearing aid microphone. This microphone measured 3" (7.5 cm) in diameter and 1¼" (2.9 or 3.1 cm) thick (which was unusually thick for a microphone. | | Click picture for larger view | | |
Close-up view of the center of the Sonotone Model 451 carbon microphone showing the Sonotone "S" logo surrounded by a ring of 12 small microphone holes. The main entrance for sounds going into the microphone wasn't these small holes, but slots around the circumference of the microphone (see below). | | Click picture for larger view | | |
Close-up of the side of the Sonotone Model 451 carbon microphone showing the microphone slots around the periphery of the microphone. They are immediately above the volume control slider knob. The earphone and battery cables plugged into the 3 pin socket at the bottom (shown unplugged). | | Click picture for larger view | | |
Close-up of the bottom front of the Sonotone Model 451 microphone showing the sliding volume control and on-off switch. Off was to the left. | | Click picture for larger view | | |
Rear view of the Sonotone Model 451 carbon hearing aid microphone showing the pocket clip (top). In the center the inscriptions read, "Sonotone", "Reg. U.S.P.O.", "U.S. Pat. No. 1811638". In the center is the serial number "178404" and below it, "Other Pats. Pend." then "Made in U.S.A." and "New York". | | Click picture for larger view | | |
Top view of the Sonotone Model 451 carbon hearing aid carbon amplifier showing the battery/earphone cable plugged in (right). This carbon amplifier was heavy for its size at 2.3 oz (66 g). | | Click picture for larger view | | |
View of the Sonotone Model 451 carbon hearing aid carbon amplifier showing the three-pin battery/earphone plug and socket. | | Click picture for larger view | | |
Side view of the Sonotone Model 451 carbon hearing aid carbon amplifier showing the two pins on the bottom that plugged directly into a battery such as the Sonotone Model X42 3-volt battery. | | Click picture for larger view | | |
Bottom view of the Sonotone Model 451 hearing aid carbon amplifier On the bottom it reads, "Pat. 2046738" and "Pat. Re. 19246". | | Click picture for larger view | | |
Close-up of the bone-conduction transducer showing the pins and sockets (unplugged). | | Click picture for larger view | | |
View of the back of the Sonotone Model 451 carbon hearing aid bone-conduction transducer with the cords plugged in and also mounted on the headband. The pins pulled out to replace the cord or transducer if necessary. | | Click picture for larger view | | |
Headband of the Sonotone Model 451 carbon hearing aid receiver with bone-conduction transducer attached. | | Click picture for larger view | | |
View of the Sonotone Model 451 carbon hearing aid in its carrying case. | | Click picture for larger view | | |
View of the inside of the carrying case lid with the faint inscription, "Sonotone Audicle". The line below reads, "Reg. U.S. Pat. Off.". | | Click picture for larger view | | |
The carrying case of the Sonotone Model 451 carbon hearing aid. The case measured 6" (15.3 cm) x 4¾" (12.0 cm) x 2" (2.5 cm).
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