Almost 40 Years of Airframe Noise Research: What Did We Achieve?

TLDR

Since the advent of low‑noise high‑bypass turbofan engines, airframe noise has become a major contributor to overall aircraft noise, with early recognition of landing‑gear and high‑lift device noise as a potential lower noise barrier, leading to extensive acoustic flight tests, wind‑tunnel experiments, and numerical studies that have identified major sources and enabled noise‑reduction technologies, though some high‑lift measures trade off aerodynamic performance. The authors aim to provide a concise survey of the achievements in airframe noise source description and reduction over the last 40 years worldwide. They review and summarize key developments in airframe noise source description and reduction, drawing on extensive acoustic testing, wind‑tunnel experiments, and numerical analyses.

Abstract

With the advent of low noise high bypass ratio turbofan engines airframe noise gained significant importance with respect to the overall aircraft noise impact around airports. Already around 1970 airframe noise, originating from flow around the landing gears and high-lift devices, was recognized as a potential “lower aircraft noise barrier” at approach and landing. Since then, the outcome of extensive acoustic flight tests and aeroacoustic wind tunnel experiments enabled a detailed description and ranking of the major airframe noise sources and the development of noise reduction means. In the last decade advances in numerical and experimental tools led to a better understanding of complex noise source mechanisms. Efficient noise reduction technologies were developed for landing gears while the benefits of high-lift noise reduction means were often compensated by a simultaneous degradation in aerodynamic performance. The focus of this paper is not on the historical sequence of airframe noise research but rather aims to provide a concise survey of the achievements in airframe noise source description and reduction over the last 40 years worldwide. Due to the vast amount of work focused on a variety of airframe noise problems, this review can only provide examples but does not claim to be complete.