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This type of noise increases with aircraft speed and also at low altitudes due to the density of the air. Jet-powered aircraft create intense noise from aerodynamics. Low-flying, high-speed military aircraft produce especially loud aerodynamic noise. The shape of the nose, windshield or canopy of an aircraft affects the sound produced. Much of ...
They reduce the forward propagating, high-pitched noise caused by the small, high-speed fan. [ 1 ] This kind of high-pitched noise is much less of an issue on modern high-bypass turbofan engines as the significantly larger front fans they employ are designed to spin at much lower speeds than those found in older turbojet and low-bypass turbofan ...
The wavelength in air of sinusoidal noise at approximately 800 Hz is double the distance of the average person's left ear to the right ear; [1] such a noise coming directly from the front will be easily reduced by an active system but coming from the side will tend to cancel at one ear while being reinforced at the other, making the noise ...
The primary sources of jet noise for a high-speed air jet (meaning when the exhaust velocity exceeds about 100 m/s; 360 km/h; 225 mph) are "jet mixing noise" and, for supersonic flow, shock associated noise. Acoustic sources within the "jet pipe" also contribute to the noise, mainly at lower speeds, which include combustion noise, and sounds ...
5.2 High-speed rotorcraft. 5.3 Hybrid-electric. 5.4 Scaled Flight Demonstrator. 6 Clean Sky 3 / Clean Aviation. 7 Research areas. ... A noise reduction for flying ...
The most fertile areas for roadway noise mitigation are in urban planning decisions, roadway design, noise barrier design, [14] speed control, surface pavement selection, and truck restrictions. Speed control is effective since the lowest sound emissions arise from vehicles moving smoothly at 30 to 60 kilometers per hour.
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The favoured engine configuration was a turbofan with very low specific thrust, i.e. very high ratio of bypass air. This gives a less effective exhaust gas velocity (lower jet noise) and therefore lower efficiency , and can be achieved in the landing phase by using a variable area final nozzle to rematch the fan .