Aircraft noise

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

Effect of Slat Gap on Farfield Radiated Noise and Correlation with Local Flow Characteristics

Abstract: Significant source noise reduction efforts are needed to cope with the "Visions 2020" of the "group of personalities" in Europe. This vision defines an aircraft noise reduction goal of 15 dB per operation until 2020, which inherently requires a reduction of airframe noise, and thus of high lift devices noise, by this same amount during landing approach. Since high lift devices noise is known to be dominant by slat noise, the aerodynamic optimization of slat-wing configurations must also account for noise aspects. Therefore the effect of slat gap variations on slat noise generation was investigated through a scale model high lift devices experimental wind tunnel study. In parallel CFD calculations (2D RANS) were performed for all test configurations to correlate measured slat noise characteristics with flow field data. Broadband slat noise levels were found to scale best with the local flow velocity at the pressure (cove) side close to the upper slat trailing-edge. Relative to the reference slat gap width a broadband noise reduction of up to 10 dB was achieved for reduced gap width (up to 15%), accompanied by an up to 4% degradation in maximum lift. For high angles-of-attack slat noise spectra were governed by a complex tone pattern, which do not follow a simple harmonic scheme but approximately scale with inflow velocity.

Inlet Noise Reduction by Shielding for the Blended-Wing-Body Airplane

Abstract: Noise shielding benefits associated with an advanced unconventional subsonic transport concept, the Blended-Wing-Body, were studied using a 4- percent scale, 3-engine nacelle model. The study was conducted in the Anechoic Noise Research Facility at NASA Langley Research Center. A high- frequency, wideband point source was placed inside the nacelles of the center engine and one of the side engines in order to simulate broadband engine noise. The sound field of the model was measured with a rotating microphone array that was moved to various stations along the model axis and with a fixed array of microphones that was erected behind the model. Ten rotating microphones were traversed a total of 22 degrees in 2-degree increments. Seven fixed microphones covered an arc that extended from a point in the exhaust exit plane of the center engine (and directly below its centerline) to a point 30 degrees above the jet centerline. While no attempt was made to simulate the noise emission characteristics of an aircraft engine, the model source was intended to radiate sound in a frequency range encompassing 1, 2, and 3 times the blade passage of a typical full-scale engine. In this study, the Blended-Wing-Body model was found to provide significant shielding of inlet noise. In particular, noise radiated downward into the forward sector was reduced by 20 to 25 dB overall in the full-scale frequencies from 2000 to 4000 Hz, decreasing to 10 dB or less at the lower frequencies. Also, it was observed that noise associated with the exhaust radiates into the sector directly below the model downstream to reduce shielding efficiency.

An overview of aircraft noise reduction technologies.

Abstract: The aim of this article is to provide a broad overview of current and future noise reduction technologies used in aircraft industries. It starts by recalling the regulation framework and the European incentives that have triggered efforts in this domain, as well as the major dedicated EU research programs. Then, technologies are introduced in four parts: engine nacelle, fan, jet and exhaust technologies and finally the airframe noise. The article concludes by giving some indications about the present capacity of these technologies to meet the noise reduction requirements and future trends to improve them.