The transmission of sound through head and throat

摘要

139,320. Drew, V. March 19, 1919. Addition to 109,708. Transmitters and receivers; sets.-Apparatus for assisting hearing comprises a sound-receiver, Fig. 1, connected to a battery and fitted with an ear piece, and a " sound terminal, " Fig. 2, worn behind the other ear and fitted with a return wire to the battery, the circuit being completed through the head of the wearer. The sound-receiver comprises a box O with ear piece P and perforated base O1 and fitted internally with a screw B, an insulated metal tube L containing iron rods K, an annular bobbin C, a disk D with serrated edge, a soft iron coil V, metal disks E, H, I, J1, and Z, springs R, S. T, a, U, hollow carbon blocks F, J containing carbon granules G, metal disks M supporting carbon rods Q forming a cage, metal domes X, Y connected by springs to the inside of the box O, and wires N connecting the disk J' to the ear-piece. The sound terminal comprises a box g perforated at top and bottom and fitted with a screw j carrying a metal disk b, spring d, drum f containing carbon granules c and a spring e. The terminal is connected by a wire i to a head band not forming part of the circuit.