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Noise Headlines and Top Story- Updated November 17, 2009
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* FAA Denies Bob Hope Bid for Mandatory Night-Time Curfew
* Europe Produces Comprehensive Noise Exposure Maps
* Beamforming Used to Isolate and Measure Noise from Truck Traffic
* Washington State DOT to Study Noise Reduction in Pile Driving
* Sound Insulation Program at MSP Proceeding on Schedule
* Airports Urge Continued Commitment to Noise Issues
* PARTNER Embarks on New Aviation Noise Research
* Noise Characteristics of Textured Road Pavements Examined
* Caltrain Working to Reduce Impact of Warning Horns
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New Study Lays the Groundwork for
Improved Aircraft Taxi Noise Modeling
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Research sponsored by FAA and the Airport Cooperative Research Program (ACRP) and carried out by Wyle Laboratories provides the basis for increasing the accuracy of airport noise prediction by incorporating noise from taxiing and other ground operations into existing and future computer models. The objective was to develop a plan for implementing a taxi noise prediction capability into the Integrated Noise Model (INM) in the near term, and eventually into the Aviation Environmental Design Tool (AEDT).
“Given that consultants are currently often asked to include predictions of aircraft noise resulting from ground operations, having a single method within AEDT/INM will ensure consistency in the implementation across various airports and studies,” according to the ACRP. “Also, it would pave the way for joint modeling of noise and emissions, considering that taxiway local air quality modeling is already implemented within FAA analysis tools.”
Although taxiway noise makes up a small portion of total aircraft noise at airports, the continued introduction of increasingly quieter aircraft and the prospect of more on-ground congestion at airports as the number of flight operations grow could increase its relative impact. “The reductions in flight noise resulting from the introduction of new engine technology are…not necessarily reflected in the noise at the low engine thrust settings that are typical of taxiing operations,” according to the project report.
Growing Impact
“Furthermore, as traffic grows, and airports approach capacity, the resulting ground congestion will mean that aircraft will be spending more time on the ground in hold short positions and waiting queues. Fuel-heavy departing aircraft will be producing more noise as they accelerate to taxiing speed from hold short positions.”
If ground operations account for a larger share of airport noise, then there will be a need to include them in estimates of future airport noise contours associated with Part 150 studies, master plans, and environmental studies required by NEPA. “This research project is designed to respond to a growing understanding that continuing reduction of noise levels related to aircraft flight operations means that previously ignored noise from aircraft ground operations, such as taxiing, now has more of an effect on nearby communities,” according to ACRP.
“Taxiing and idling in runway queues, especially during peak hour operations or at night, can significantly contribute to noise contours and day-night average sound levels. This is particularly true when taxiways are very close to the airport property lines and near neighborhoods or other noise sensitive locations.”
Sensitivity Studies Conducted
Wyle conducted a comprehensive series of acoustic sensitivity studies with measurements taken at Reagan Washington National, Washington Dulles International, and T.F. Green airports that separated taxiing noise into three elements for further study: engine source noise (level, spectra, and directivity); aircraft movements and operating states (location, duration, and power setting); and environment/propagation (lateral attenuation, terrain, shielding, and ground impedance).
“The sensitivity studies revealed that the primary weakness for taxi noise modeling is related to engine source noise modeling,” concluded Juliet Page, the principal investigator. Other findings and conclusions are:
• the existing source directivity model in INM needs to be modified to more appropriately account for taxi operations;
• at present there is sufficient capability in INM to support aircraft movements and operating states from gate to runway, terminal to runway, or via time-in-mode assignments;
• future aircraft movement and queuing modeling improvements targeted for AEDT will greatly reduce the current user input burden in INM;
• the propagation algorithm (primarily lateral attenuation in INM) is sufficient and only site-specific airport considerations will necessitate the inclusion of terrain, shielding and/or variable ground impedance;
• acoustic and flight data recorder data were not gathered concurrently, therefore one could not definitively determine the noise level for a particular taxi engine thrust or the sensitivity of noise with changes in thrust.
“The need for concurrent acoustic and engine operating state data is an important finding of this study and is the primary reason for considering only a nominal taxi state in the short term, and the recommendation of a comprehensive long term solution seeking concurrent taxi noise and operating condition measurements for the purposes of developing an enhanced acoustic sensitivity to thrust capability for AEDT,” according to the report.
“We found that taxi noise can result in a ‘significant impact’ (DNL increase of more than 1.5 dB) under certain conditions, and hence suggest short term implementation in INM, so that an improved taxi modeling capability may be provided to the noise modeling community sooner rather than later.” Wyle estimates the cost of implementing a taxi noise capability in INM is $220,000; in AEDT alone $240,000; and in both, $310,000, including approximately $130,000 for development of the various aircraft and acoustic taxi databases.
Copyright 2009 Great Circle Communications LLC. No unauthorized posting, forwarding, or any other form of transmission of this material, by any means, in whole or in part, is allowed.
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