| 摘要 |
Provided is an insertion type earphone, in which a receiver unit (12) is constituted to have a receiver body (50) (or a BA type receiver) housed in a casing (20). The receiver body (50) includes a housing (56) having a small hole (66a) formed to provide communication between a back space (CR) and the external space. The casing (20) is constituted to include a cylindrical frame (32) having a sound guide tube (16) at its leading end portion and a gasket (36) inserted from a root end portion and fixed in the cylindrical frame (32). The receiver body (50) is so inserted into and fixed in the gasket (36) as to isolate a sound releasing hole (64a) and the small hole (66a). In the gasket (36), a communication hole (36e) is formed to provide communication between the sound releasing hole (64a) and a sound way (16a) of the sound guide tube (16). Between the receiver body (50) and the casing (20), moreover, a back pressure adjusting first closed space (C1) is formed to communicate with the small hole (66a) but isolated from the sound way (16a), thereby to retain the auditory volume feeling in a low sound range sufficiently in the insertion type earphone having the BA type receiver.
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