ASSUMED NOISE LEVEL IN CREW CABIN OF AIRCRAFT WITH EXTRA-HIGH BY-PASS RATIO ENGINES/CALCULATION, ESTIMATE OF EFFECT, METHODS OF REDUCTION

摘要

Task of aircraft compliance with new noise level environmental standards required revision of technical approaches one of which is tendency to switch to extra high bypass ratio engines (from 2.5 … 5.0 to 8 …12). The long-term researches have allowed essentially to specify calculated models of modern aviation designs in frequency range of engines rotors rotation and to determine the tendency of dynamic characteristics changing (for example, engine by increase of its by-pass ratio). On the base of obtained characteristics (frequency characteristics of dynamic compliance and function of vibroacoustic conductivity of engine bodies and airframes) noise analysis was performed at various levels of engine vibration effects. Possibility of high-level low-frequency noise components in crew cabin was highlighted even at operational level of engine vibration. The increased level of infrasound constituent of noise in the cockpit in comparison with passenger cabin was fixed by the research program and it gives some concern by transfer to engines of high bypass ratio because part of infrasound constituent has tendency to extension.