GB1082541A - Improvements in or relating to telephone receivers - Google Patents

Abstract

1,082,541. Head-sets; sound modifying devices. AIRMED Ltd. Oct. 26, 1964 [Nov. 5, 1963], No. 43686/63. Headings H4J and H4X. A miniature telephone receiver 4 (Fig. 2) is connected by a sound tube 7 to a resonance chamber 12 (Fig. 3) and an acoustic transmitter 9. The transmitter 9 is of approximately the same size as the outer ear and is arranged to be supported close to a listener's ear when in use. The resonance frequencies of the tube 7 and chamber 12 are related to the frequencyresponse characteristic of the receiver 4 to give a resultant frequency response better than that of the receiver 4 alone. A head-set (Fig. 1, not shown) having a boom carrying a microphone has two such arrangements, one for each ear. The open end of each transmitter 9 is closely adjacent or presses against the ear. Each tube 7 is held by a liner 14 formed with a channel 15. Holes 16 in the tube 7 and channel 15 permit sound transmission to the cavity 12. The cavity 12 has an apertured partition tuned on the Helmholtz principle and is tuned to a lower or higher frequency than the resonant frequency of the tube 7. A further resonant cavity (not shown) may be added. The tube 7 is in two parts united by a joint 10 for ease of manufacture and is attached to a socket 6 in a box 2 containing the receiver 4 by a universal joint comprising a pierced ball 8.