Noise emissions from commercial aircraft

Aircraft noise ¹ is an aerodynamically generated phenomenon, a byproduct of the interaction of the airstream with the various engine and airframe components as well the flow processes within an aircraft's engine exhaust plume. These interactions and processes generate pressure fluctuations in the ambient atmosphere that radiate away from the aircraft as noise. The portion of the aircraft noise that reaches the ground affects the populated communities and is the topic of this chapter. ² depending on the particular airframe or engine component, and the nature of its interaction with the airstream, tone and broadband noise is generated over a wide range of frequencies. Aircraft noise is the amalgam of these various component noise contributions whose relative intensities are dictated by the engine architecture and power level as well as the airframe design and whether or not the landing gear and/or the high-lift devices (i.e., the flaps and slats) are deployed. Figure 1.1 lists some of the important sources of aircraft noise during the landing approach for large commercial jet aircraft. depending on the type of aircraft, not all of these noise sources may be present or significant. The various aircraft noise sources and their relative importance will be discussed later in this chapter.