Date: 11 Nov 2003
Time: 09:56
QinetiQ and Ultra Electronics are poised to achieve a world first by combining active and passive technology to reduce a broad spectrum of aircraft cabin noise.
'Broadband noise', which originates from the airflow over the fuselage of the aircraft, can be transmitted through the structure and panels into the aircraft interior. The AIRAT (Active Isolator Research for Aircraft Trim panels) system involves attaching aircraft trim panels to the airframe using a new hybrid mount that incorporates both active and passive elements. By attacking this transmission path and reducing the panel vibration, the new mounts can achieve substantial reductions in internal cabin noise levels.
Researched and developed by scientists at QinetiQ, this technology is the result of a seven-year study funded by the DTI. Laboratory tests performed on synthetic trim panels indicate an improvement in performance over existing mounts of at least 10 decibels. A ground-based demonstrator will be available later this year and a full flight demonstration is planned for early 2004.
Passive isolation of the panel provides good performance at higher frequencies, however maintaining that performance at lower frequencies would involve a serious weight or size penalty. By combining passive and active technology, this low frequency problem has now been resolved. The hybrid approach adopted provides the opportunity to optimise the passive element, with the focus now on its high frequency performance. This has led to an innovative design for that element. Combined with the active system, the new mount has the potential to provide reduced transmission compared with existing mounts over the entire range of audio frequencies.