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The Noise From Aircraft
Published online by Cambridge University Press: 28 July 2016
Extract
A general expression is obtained for the potential of sound or aerodynamic disturbance from a source moving with variable vector velocity, based on linear theory. Knowing the space time curve for the source, the Doppler frequency corrections and intensities can be determined. If in any part of its trajectory the aircraft exceeds the velocity of sound, the number of sonic bangs and the times of occurrence can be calculated. A numerical example is given. The following conclusions are deduced: (i) If at any point of its trajectory, the component of the aircraft velocity in the direction of the observer is equal to the velocity of sound, a sonic bang is propagated to the observer with the velocity of sound. This has been previously postulated by C. H. E. Warren. (ii) A bang as determined by conclusion (i) comprises two components and in certain circumstances the components in some of the bangs may be acoustically separable, thus giving rise to double bangs.
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- Copyright © Royal Aeronautical Society 1954