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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 the noise of a propeller aircraft is of aerodynamic origin due to the flow of air around the blades.
Detailed information on measurement of aircraft acoustic signature to meet the requirements of Annex 16 is found in ICAO Document 9501 [5] and IEC 61265. [6] Data acquisition in one-third-octave bands is required, followed by processing to yield a logarithmically-scaled value in decibels relative to a sound pressure of 20 micropascals for each one-third-octave band.
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 ...
Noise may be measured using a sound level meter at the source of the noise. [23] [24] [25] Alternatively, an organization or company may measure a person's exposure to environmental noise in a workplace via a noise dosimeter. [26] The measurements taken using either of these methods will be evaluated according to the standards below.
Landing quota count values are based on the certificated approach noise level at maximum landing weight minus 9.0 EPNdB. Aircraft were originally divided into six QC bands from 0.5 to 16, but following a review by the Department for Transport [ 1 ] a seventh category – Quota Count 0.25 – was added in March 2007 [ 2 ] and an eighth category ...
The FAA also pursues a program of aircraft noise control in cooperation with the aviation community. [112] The FAA has set up a process to report for anyone who may be impacted by aircraft noise. [113] The Federal Highway Administration (FHWA) developed noise regulations to control highway noise as required by the Federal-Aid Highway Act of ...
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While hush kits effectively reduce noise emissions from older aircraft, noise cannot always be reduced to the level of modern planes at a reasonable cost. [ 7 ] In 1999, this concern led to a regulatory dispute between the United States and the European Union , where the EU proposed a new noise ordinance which effectively prevented the use of ...