| 摘要 |
An active noise reducing headphone (10) comprising: an ear piece (102) configured to couple to a wearer's ear to define an acoustic volume comprising the volume of air within the wearer's ear canal and a volume within the ear piece; a feed-forward microphone (108) acoustically coupled to an external environment and electrically coupled to a feed-forward active noise cancellation signal path; a feedback microphone (106) acoustically coupled to the acoustic volume and electrically coupled to a feedback active noise cancellation signal path; an output transducer (104) acoustically coupled to the acoustic volume via the volume within the ear piece and electrically coupled both to the feed-forward and feedback active noise cancellation signal paths; and a signal processor configured to apply filters and control gains of both the feed-forward and feedback active noise cancellation signal paths; wherein the signal processor is configured to: operate the headphone in a first operating mode providing effective cancellation of ambient sound and in a second operating mode providing active hear-through of ambient sounds, during the second operating mode, detect high-frequency signals in the feed-forward active noise cancellation signal path exceeding a threshold level indicative of abnormally high acoustic coupling of the output transducer to the feed-forward microphone, in response to the detection, apply a compressing limiter to the feed-forward signal path, and once the high-frequency signals are no longer detected at levels above the threshold, remove the compressing limiter from the feed-forward signal path. |
