The horizontal propagation of sound from a jet engine close to the ground, at Hatfield

Abstract

A previous paper reported the results of a series of measurements of the horizontal propagation of sound over grassland at Radlett. The main factors found to influence the propagation were the vector wind and ground absorption losses. The temperature gradient had a smaller effect, the propagation losses in summer being greater than in winter. The experiment was repeated at a different site, at Hatfield, to determine whether the ground losses were peculiar to the ground at Radlett and also to make measurements after dark, under conditions of temperature inversion. The results of the second series of measurements are given in this present paper. The ground absorption losses were slightly less and occurred at a higher frequency than at Radlett. The effect of the vector wind on the propagation was very similar to that found at Radlett and the change in propagation losses between the temperature gradient conditions—lapse, neutral and inversion—at Hatfield was an extension of the change between summer and winter at Radlett.