Patent ID: 7317802

Claim:
An active-noise-reduction (ANR) system for a user having a head, an ear, and mouth, the system comprising: an ear cup for placement over the ear and against the head of the user, with the earcup having an ANR driver positioned between a back cavity in the earcup and a front cavity in the earcup, the front cavity adjacent the ear of the user when the earcup is placed over the ear; an ANR microphone positioned within the earcup; ANR closed-loop control circuitry coupled to the ANR driver and the ANR microphone; a boom microphone coupled to the ANR closed-loop control circuitry; and means for limiting effect of user fit variations on stability of the ANR closed-loop control circuitry, with the means including a substantially user-invariant air passage in fluid communications with the front cavity and an exterior of the earcup.