05276740 is referenced by 60 patents and cites 8 patents.

An earphone device includes an acoustic tube having an inner diameter substantially identical to that of the external auditory canal has an ear mounting portion at one end and an acoustic non-reflecting portion at the outer end. An earphone unit and an internal microphone unit are mounted on the periphery of the acoustic tube adjacent each other and communicate with the interior of the acoustic tube with their respective vibration plates facing inwardly of the tube. The phase of the signal representing the external noise in the acoustic tube picked up by the internal microphone unit is reversed and combined with the audio signal fed to the earphone unit. The earphone device also includes an external microphone unit on the outside of the acoustic tube and a variable ratio mixing circuit for mixing the input audio program signal, the reversed phase signal obtained from the internal microphone unit, and the signal from the external microphone unit, so that external sounds can be heard without removing the earphone device.

Title
Earphone device
Application Number
762028
Publication Number
5276740
Application Date
February 16, 1993
Publication Date
January 4, 1994
Inventor
Akira Kimura
Kanagawa
JP
Yasuhiro Iida
Tokyo
JP
Hiroyuki Sogawa
Kanagawa
JP
Kiyofumi Inanaga
Kanagawa
JP
Agent
Jay H Maioli
Lewis H Eslinger
Assignee
Sony Corporation
JP
IPC
H04R 1/10
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