This paper provides an overview of the aircraft noise. The classical noise units and these appropriate to quantify the annoyance related to aircraft and engine noise are shortly recalled. These units are necessary to explain the rules and levels of aircraft regulation. The main noise sources are the jet at the engine exhaust, the compressor and the fan. The jet noise increases very fast with higher jetvelocity. The efficiency of the engine on subsonic transport aircraft requires high bypass ratio engines to obtain low jetvelocities. This has of course a favorable effect on the noise level of the jet. But increasing the airflow through the fan and the fandiameter will augment the noise generated by this fan. The fan and the compressor noise can be reduced by appropriate rotor and stator design, blade and vane numbers, rotation speed of the rotor, spacing between vane and blade row, absorption by lining the inlet and outlet ducts. But many older aircraft with low bypass ratio engines, which do not comply to the latest noise rules (chapter 3 of ICAO rules) have still several years to fly. It is very expensive to re-engine the aircraft with the most modern engines. Hush-kitting the old engines to comply with the noise rules can be economically justified. To conclude this overview the problems and possibilities of hush-kitting are explained. The aerodynamic noise generated by the airframe, the wings and flaps, the landing gear is of less importance. Even if this noise is not negligible in the case of a heavy transport aircraft, it will not be treated in this paper.
Aircraft engine noise quantities, noise sources and alleviation
Größen, Quellen und Verminderung der Schallabstrahlung von Flugzeugtriebwerken
European Journal of Mechanical Engineering ; 39 , 4 ; 195-218
1994
24 Seiten, 73 Bilder, 18 Quellen
Aufsatz (Zeitschrift)
Englisch
Schallemission , Schallquelle , Lärmminderung , Schallstärke , Flugzeugtriebwerk , Richtlinie , Abgasströmung , Verdichter , Gebläse , Fluggeschwindigkeit (Luft) , Transportflugzeug , Bypassturbine , Strömungsvorgang , Konstruktionsdaten , Drehzahl , Absorption , Aerodynamik , Flugzeugzelle , Tragwerk (Flugzeug) , Gesetz (Recht)
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