The disturbance due to aircraft noise which is being experienced in residential areas around the world's major airports is generally recognised as a serious problem. Indeed, the problem has reached the stage where public reaction is already influencing the development of future aircraft. Such influence may be seen in current international intention to include noise limitations in the certification of aircraft.
Limits imposed on the noise generated by aircraft engines should serve to prevent the problem from becoming catastrophic, but cannot be expected to provide a final solution. Aircraft manufacturers may seem confident that further improvements in performance could be achieved without corresponding increase in noise, but further increases in air traffic could cancel out these gains and still leave communities near airports excessively disturbed.
A proposed technique for measuring the noise of a ducted fan by means of a microphone placed inside the fan duct was evaluated by comparing results so obtained with those obtained by measuring the total sound energy radiated from the duct into a reverberation chamber. A suitable microphone windscreen was developed and was used to reduce the aerodynamic self-noise generated by the microphone to a negligible minimum. Good correlation was obtained, and by studying transverse resonance conditions in a duct it was attempted to show how suitable microphone stations could be found to eliminate measuring errors caused by the existence of standing waves.Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 128.42.202.150 On: Tue,
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