GB1495292A - Acoustic transmission systems for electro-acoustic transducers - Google Patents

Abstract

1495292 Deaf aids; headsets INDUSTRIAL RESEARCH PRODUCTS Inc 25 Nov 1974 [20 Feb 1974] 50882/74 Heading H4J [Also in Division G2] In using an elongated tubular passage to couple acoustically between a sound opening and an electro-acoustic transducer, a uniform frequency response is obtained by providing an elongated tubular branch passage acoustically closed and damped and such as to exhibit at its junction with the main passage an impedance variation complementary to that of the main passage. This can be used with microphones or receivers and be applied in deaf aids or headsets. Fig. 10 shows the coupling of a deaf aid receiver and an ear cavity by way of a common receiver duct R and a main duct M; an auxiliary duct X closed by a plug and having damping D providing compensation for impedance variations attributable to the duct M as seen from the receiver. A behind-the-ear hearing aid (Fig. 4) has a mould housing 13 connected by a hook portion 17 through flexible tubing 19 to an ear mould 21. A receiver 15 is coupled by tubing 23 to a T-junction 25 and thence by duct 27 to the ear mould, a tube 31 with a folded extension plugged at 35 providing the compensating branch. Damping elements are placed in arms of the T-junction. Alternative ways of providing the coupling in behind-the-ear hearing aids are described with reference to Figs. 7 and 8, not shown. Fig. 6 shows a spectacles-type hearing aid in which the plugged compensating branch tube is provided in the temple piece 43, damping elements 28, 29 being provided in a connector 45. In Fig. 5 a microphone 4a is housed in a temple piece 5 1 of a spectacle, sound ducts 19A, 27A, 23A being formed when the two moulded halves of the temple piece are joined face-to-face; damping elements 28, 29 being incorporated.