04455675 is referenced by 148 patents and cites 3 patents.

Headphones have a small cavity between the diaphragm and the ear canal with a microphone in the cavity closely adjacent to the diaphragm providing a feedback signal that is combined with the input electrical signal to be reproduced by the headphones to provide a combined signal that is power amplified for driving the diaphragm.

Title
Headphoning
Application Number
6/372471
Publication Number
4455675
Application Date
April 28, 1982
Publication Date
June 19, 1984
Inventor
John Carter
Cambridge
MA, US
Amar G Bose
Wayland
MA, US
Agent
Charles Hieken
Assignee
Bose Corporation
MA, US
IPC
H04R 1/10
View Original Source