Active noise cancellation system with orientation sensor to determine ANC microphone selection

摘要

Portable radio handset (1) comprising master unit (3) connected to slave unit (5) with first and second microphones (9,11) operating as primary and secondary microphones in an active noise cancellation (ANC) system depending on the orientation of the slave unit which is detected using an orientation sensor (13). First and second microphones are interchangeable so either can operate as the primary or secondary microphone. Orientation sensor may comprise an accelerometer, tilt switch, gyroscope, or manually-operated switch. First and second microphones may be mounted at either end and/or side of the slave unit. A visual indicator (LED) may show which microphone is operating as the primary microphone. Orientation sensor may enter a configuration mode for a predetermined time period, with fixed orientation set on time expiry, until re-configuration (reset or next start-up). Primary microphone may the one closest to the users mouth, with secondary microphone sensing ambient background noise. The system is intended for use in the portable radio handsets used by the emergency services (police, fire, ambulance / paramedics) for clear, high quality audio communication with control centre dispatchers. Master unit may be worn on a belt around the waist with slave unit attached to the chest region.