Aircraft noise

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

Interior noise considerations for advanced high-speed turboprop aircraft

Abstract: This paper describes recent research on noise generated by high-speed propellers, on noise transmission through acoustically treated aircraft sidewalls, and on subjective response to simulated turboprop noise. Propeller noise discussion focuses on theoretical prediction methods for complex blade shapes designed for low noise at Mach = 0.8 flight and on comparisons with experimental test results. Noise transmission experiments using a 168-cm-diam aircraft fuselage model and scaled heavy-double-wall treatments indicate that the treatments perform well and that the predictions are usually conservative. Studies of subjective comfort response in an anechoic environment are described for noise signatures having combinations of broadband and propellertype tone components.

Electric Motor Noise from Small Quadcopters: Part 1 - Acoustic Measurements

Abstract: There is increased interest in using electric motors to drive propulsors across a range of small air vehicle classes. Applications include both vertical lift and conventional takeoff and landing systems for Small Unmanned Aircraft Systems. Mission profiles call for integrating these systems into urban airspaces exposing populated areas to new noise sources. In addition to the propulsor noise from rotors and propellers, electric motors are expected to contribute to the overall sound levels and possibly human annoyance. This work presents acoustic measurements of electric motors used for small quadcopters to characterize the sound and identify sources with and without a propeller. Free field microphone measurements were used to determine directivity and a phased microphone array was used to identify sound sources. A companion paper (Part II - Source Characteristics and Prediction) compares the far field results with current probe measurements of the signal driving the motor, the structural response of the motor case, and describes prediction methods of electric motor noise.

Examination of the Lateral Attenuation of Aircraft Noise

Abstract: Measurements of the lateral attenuation of noise from aircraft operations at Denver International Airport were made at distances up to 2000 feet and elevation angles up to 27 degrees. Attenuation Calculated from modem ground impedance theory agrees well with average measured attenuation. The large variability between measured and predicted levels observed at small elevation angles is demonstrated to be due to refraction by wind and temperature gradients.

Air traffic assignment based on daily population mobility to reduce aircraft noise effects and fuel consumption

Abstract: The paper first investigates the influence of daily mobility of population on evaluation of aircraft noise effects. Then, a new air traffic assignment model that considers this activity is proposed. The main objective is to reduce the number of people affected by noise via lowering as much as possible the noise exposure level Lden of individuals or groups of people who commute to the same locations during the day. It is hereby intended to reduce the noise impact upon individuals rather than to reduce the impact in particular – typically densely populated – areas. However, sending aircraft farther away from populated regions to reduce noise impact may increase fuel burn, thus affecting airline costs and sustainability . Therefore, a multi-objective optimization approach is utilized to obtain reasonable solutions that comply with overall air transport sustainability. The method aims at generating a set of solutions that provide proper balance between noise annoyance and fuel consumption. The reliability and applicability of the proposed method are validated through a real case study at Belgrade airport in Serbia. The investigation shows that there is a difference between the number of people annoyed (NPA) evaluated based on the census data and the NPA evaluated based on the mobility data. In addition, these numbers differ significantly across residential locations. The optimal results show that the proposed model can offer a considerable reduction in the NPA, and in some cases, it can gain up to 77%, while maintaining the same level of fuel consumption compared with the reference case.

Optimization of Annular and Cylindrical Liners for Mixed Exhaust Aeroengines

Abstract: The increase in bypass ratios for modern day turbofan engines has led to fan rearward broadband noise emerging as one of the principal aircraft noise sources. The most widespread method for mitigating this noise source is the installation of acoustic liners in the ducting downstream of the fan. Mixed exhaust designs have the potential to be quieter than a three quarter cowl aeroengine due to the additional surface available for liner application. As a result, the Silent Aircraft concept design contains an embedded distributed propulsion system to exploit this opportunity. This paper outlines a suitable method for optimizing the annular and cylindrical liners that make up the exhaust system. To gain maximum benefit, liners should be designed to absorb the modal disturbances that are the most significant for an observer on the ground. The optimization uses an advanced noise footprint cost function to achieve this. Consequently, the liners and the length of the installation have been chosen to meet the aggressive noise target set for the aircraft. In addition, we explore the effect that modal scattering between axial liner junctions can have on the acoustic performance of the system. We find that energy interchange between radial modes will often have a detrimental effect on the overall attenuation, although this can be addressed by selecting the order of the liners in a more considered way. The assumption that scattering between liners can be neglected during optimization to allow design of the individual components therefore appears to be valid in this case. However, subsequent attention has to be directed to the order in which they are placed. Current and next generation mixed exhaust aeroengines will be restricted to smaller liner segment lengths than the Silent Aircraft. This analysis suggests that scattering and hence liner order is likely to more important for these designs.