Community Research and Development Information Service - CORDIS

Reduction of helicopter interior noise

The possibility of reducing low frquency interior noise in helicopters by up to 12 dB by active noise control has been validated in flight. In this range of frequencies it is very impractical to apply conventional passive treatment.

Methods to identify noise transmission paths and vibratory source descriptors have been validated in flight demonstrating that gearbox noise dominant transmission path is structure borne.

The potential benefits of actively controlling the transmissibility of gearbox support struts (as well as passive means such as tuned resonator and elastomeric bearings) and structural panels have been demonstrated. The combination of active control and elastomeric bearings showed a reduction of up to 40 dB in the transmissibility of the strut.

A predictive SEA code has been developed and validated on a real helicopter fusilage.

A study on the characterization of the most influential parameters (including errors and mis alignements) in noise emission byb gears has been performed.

Reported by

Agusta SpA
Via Schiaparelli
21013 Gallarate Varese
Italy
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