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Content archived on 2024-04-19

Reduction Of Helicopter Internal Noise

Objective

The primary aim of the RHINO project is to reduce the interior noise of helicopters whilst at the same time minimizing the weight of any control mechanism.
The following results have been achieved:
The possibility of reducing tonal low frequency interior noise in helicopters by up to 12 dB with Active Noise Control has been demonstrated for the first time in flight.
Methods to identify noise transmission paths and vibratory source descriptors have been validated in flight, demonstrating that gearbox noise dominant transmission path is structureborne.
The potential benefits of actively controlling the transmissibility of gearbox support struts (as well as passive means such as a tuned resonator and elastomeric bearings) and structural panels have been lab-demonstrated. The combination of active control and elastomeric bearings showed a reduction of up to 40dB in the transmissibility of the strut, while panel control achieved up to 15dB reductions in radiated noise.
A predictive SEA code has been developed and lab validated on a real "green" helicopter fuselage.
A study on the characterisation of the most influential parameters (including errors and misalignments) in noise emission by gears has been performed.
A reference noise level of 75 dBA has been identified by the European helicopter manufacturing industries as realistically achievable within a time scale of 5 years.

The objective of this project is to approach the noise reduction problem on helicopters following a global and systematic way.

Any noise control strategy will deal with three different areas: the sources, the transmission path and the receiving space.

First it will be necessary to quantify the sources, identify the path by which the source energy travels to the cabin and obtain an understanding of the mechanisms involved.

Secondly it is necessary to develop new and improve technologies leading to substantial noise reductions and to validate the technological advances by using either flight demonstrator or proof-of-concept laboratory experiments.

Finally as part of the overall strategy to reduce noise, it is important to develop a noise prediction capability. This will enable initial helicopter design to be optimized for minimum noise and will also allow the assessment of noise reduction requirements at an early design stage.

Topic(s)

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Call for proposal

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Coordinator

Agusta SpA
EU contribution
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Address
Via Giovanni Agusta 520
21017 Cascina Costa di Samarate Varese
Italy

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Total cost
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Participants (12)