Aircraft noise

About: Aircraft noise is a research topic. Over the lifetime, 3051 publications have been published within this topic receiving 32039 citations.

Potential for Landing Gear Noise Reduction on Advanced Aircraft Configurations

Abstract: The potential of significantly reducing aircraft landing gear noise is explored for aircraft configurations with engines installed above the wings or the fuselage. An innovative concept is studied that does not alter the main gear assembly itself but does shorten the main strut and integrates the gear in pods whose interior surfaces are treated with acoustic liner. The concept is meant to achieve maximum noise reduction so that main landing gears can be eliminated as a major source of airframe noise. By applying this concept to an aircraft configuration with 2025 entry-into-service technology levels, it is shown that compared to noise levels of current technology, the main gear noise can be reduced by 10 EPNL dB, bringing the main gear noise close to a floor established by other components such as the nose gear. The assessment of the noise reduction potential accounts for design features for the advanced aircraft configuration and includes the effects of local flow velocity in and around the pods, gear noise reflection from the airframe, and reflection and attenuation from acoustic liner treatment on pod surfaces and doors. A technical roadmap for maturing this concept is discussed, and the possible drag increase at cruise due to the addition of the pods is identified as a challenge, which needs to be quantified and minimized possibly with the combination of detailed design and application of drag reduction technologies.

Evaluation of Ride Quality Prediction Methods for Helicopter Interior Noise and Vibration Environments

Abstract: The results of a simulator study conducted to compare and validate various ride quality prediction methods for use in assessing passenger/crew ride comfort within helicopters are presented. Included are results quantifying 35 helicopter pilots discomfort responses to helicopter interior noise and vibration typical of routine flights, assessment of various ride quality metrics including the NASA ride comfort model, and examination of possible criteria approaches. Results of the study indicated that crew discomfort results from a complex interaction between vibration and interior noise. Overall measures such as weighted or unweighted root-mean-square acceleration level and A-weighted noise level were not good predictors of discomfort. Accurate prediction required a metric incorporating the interactive effects of both noise and vibration. The best metric for predicting crew comfort to the combined noise and vibration environment was the NASA discomfort index.

Noise Reduction Efforts for Special Operations C-130 Aircraft Using Active Synchrophaser Control

Abstract: : Aircraft noise often inhibits mission effectiveness. As a result, flight crews, ground maintenance personnel, and passengers suffer degraded voice communication, impaired performance, increased fatigue, and hearing loss. In an effort to reduce the level of noise both inside and outside of the aircraft, techniques have been developed that attempt to quiet the environment. The simplest approach uses passive noise reduction methods, including installing acoustic insulation and exhaust modifications, but these only provide limited success. A more complicated approach uses an active noise cancellation (ANC) system, which offers improved performance that can augment passive methods to significantly reduce both internal and external aircraft noise. ANC achieves noise reduction by creating an anti-noise, which is an equal and opposite acoustic wave that cancels the unwanted noise. This type of cancellation works well in smaller volumes, like headset ear cups. For larger volumes or environments, arrays of loudspeakers are needed, but are often ineffective due to their size and weight. Since the primary noise on multi-engine turboprop aircraft, such as the C-130, originates from the engine-propeller system, the noise from one engine-propeller can be tuned to provide a canceling acoustic wave to reduce the noise generated from another engine-propeller on the same aircraft. Because the levels of noise generated from each engine-propeller combination are similar under normal operating conditions, a means to adjust the propeller phasing to create a noise canceling effect is needed. For multi-engine propeller-driven aircraft, engine-propeller phase control is accomplished using an electromechanical device called a synchrophaser. To optimally control the phase angle relationships among the four engine propellers, a controllable or active synchrophaser system is needed. The synchrophaser system described in this paper is a joint effort between AFRL and AFSOC.

Techno-economic and environmental risk assessment of innovative propulsion systems for short-range civil aircraft

Abstract: Aircraft are thought to contribute about 35% (IPCC, 1999) to the total radiative forcing (a measure of change in climate) of all the human activities and this figure is forecaste to increase Future concerns for aviation’s role in climate change are mainly due to the envisaged continued growth in this sector Growth rates for emissions are less than those for traffic growth since fuel efficiency continues to improve over the years Despite regular improvements in fuel efficiency, emissions will carry on increasing and several solutions need to be found The growth of air travel as well and its effect on world economics is hampered by local opposition to aircraft noise Besides, restrictions on night take-off and landing because of aircraft noise levels leads to a negative impact on the revenues of Europe’s airlines and often results in non-European over-night airport refuelling stops According to ACARE (Strategic Research Agenda, 2005), the sustainable development of air transport depends on achieving a significant across-the-board reduction in environmental impact, in terms of greenhouse gases, local pollution and noise around airports Over the past 40 years the introduction of new technology has mitigated the environmental impact of aviation growth, but at the expense of increasing operating costs Consequently, in order to make aviation more sustainable environmentally and economically, radically innovative turbofans need to be considered and optimised at the aircraft level Based on the above, this PhD project addresses the following research questions: • The potential of different novel propulsion systems with enhanced propulsive efficiency (using advanced, contra-rotating and geared turbofans) and thermal efficiency (using intercooled and recuperated, and constant volume combustion turbofans) to meet future environmental and economical goals • The trade-offs to be made between noise, emissions, operating cost, fuel burn and performance using single- and multi-objective optimisation case study In order to achieve this, a multidisciplinary design framework was developed which is made up of: aircraft and engine performance, weight, cost, noise, emissions, environment, and economics and risk models An appropriate commercially available optimiser is coupled with this framework in order to generate a powerful aero-engine preliminary design tool The innovative turbofans were benchmarked against the baseline turbofan at the aircraft level using the A320 The multi-objective trade case study for minimum fuel burn, NOx emissions, engine direct operating cost (DOC) and noise proves that these engines are feasible to meet future noise and emissions requirements for an acceptable cost of ownership The key driver to lower engine DOC is a considerable fall in fuel consumption Nevertheless, acquisition and maintenance cost rise owing to hardware complexity Consequently, further study of these engines is recommended as their environmental performance potential is considerable