05033090 is referenced by 68 patents and cites 10 patents.

In a hearing aid with a microphone, an amplifier and a receiver supplying amplified sound to the user, a second signal path is provided comprising a second, feedback-suppressing microphone, placed at a location to receive feedback-causing sound from the receiver. The output of second provided microphone is suitably attenuated and delayed by an amount .DELTA.t corresponding to the effective acoustical distance a+b between the second microphone and the main microphone and supplied to a difference amplifier in opposition to the signal from the main microphone. Thus, the component of the signal from the main microphone likely to cause positive feedback or "howling" is substantially cancelled out. In another embodiment, the feedback-suppressing signal path is an acoustical path comprising a tube leading to a rear cavity in a microphone of the directional or differential type.

Title
Hearing aid, especially of the in-the-ear type
Application Number
322387
Publication Number
5033090
Application Date
September 4, 1990
Publication Date
July 16, 1991
Inventor
Soren Weinrich
Espergaerde
DK
Agent
Larson & Taylor
Assignee
Oticon
DK
IPC
H04R 25/00
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