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Content archived on 2024-04-30

Reduction of aircraft noise by nacelle treatment and active control


Objectives and content:

Community reaction to aircraft noise is now recognised as one of the most important constraints limiting future growth of air transport industry unless all future aircraft noise levels decrease in such a manner to offset the effect of air traffic growth on noise exposure. The RANNTAC programme, together with the RESOUND programme on engine noise source reduction technology and the RAIN programme on the reduction of airframe and installation noise are the three main and complementary pieces of the proposed R & D effort co-ordinated at European level by the X-NOISE thematic network on external noise. This effort is needed to meet the requirements expressed in the EU consultation paper of November 96 for reduction in aircraft noise levels and accept the US implicit challenge a complying with much more stringent noise rules in the early 2000's.The objective of the combined programme is to deliver within 8 year, aircraft environmental noise abatement of 6 decibels both at departure from airports and at arrival relative to current technology demonstrated by aeroplane industry. The objective of RANNTAC is to acquire the technology necessary to support the development and manufacturing of turbofan engine nacelles featuring noise reduction devices and designs enabling to achieve up to 4 dB attenuation on engine internal noise sources in addition to that achieved by currently produced acoustic liners.

Half this noise reduction will be demonstrated at the end of the programme while the means to achieve the reminder will be identified and defined for further large-scale demonstration. The practical results of the proposed research is to secure the design capabilities of developing in future transport aircraft nacelles, a large range of novel sound absorbing liners, air intake shapes allowing to control the fan noise radiation and in duct active noise control systems. The work programme will provide theoretical and experimental acoustic evaluation of all proposed systems and concepts in the context of real nacelle duct environment and assessment of the expected benefits on future aircraft noise together with the chances of industrial application and foreseen impaction aircraft economics.

The programme's structure features three tasks:
Specifications, Assessments, Exploitation and Management;
Development of novel nacelle treatment concepts;
Development of Active Noise Control technology in nacelles.

The work will be essentially carried out in parallel in tasks 2 an 3, each of them developing and providing in the end a panel of noise reduction solutions of different types, every type being evaluated on appropriate common testfacilities. BE97-4121

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EU contribution
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Route de Bayonne 316

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Participants (21)