Abstract
LONDON Physical Society, June 2. C. F. B. KEMP: Observations on the intensity of low-frequency sounds close to a metal airscrew. A condenser transmitter and continuously recording cathode ray tube have been used to obtain the wave-form of the sound from a metal airscrew operating at zero rate of advance. Fourier analysis has been applied to records taken at various distances up to 300 ft. from the airscrew and the rate of decay of intensity has been determined for the first three harmonics. At distances greater than 100 ft. the inverse-square law of distance has been found to hold, but at nearer points the rate of decay is not constant and varies in a complicated manner. W. M. HAMPTON: The visibility of objects in a searchlight beam. The discussion is divided into three parts dealing separately with the light reflected by the object from the incident beam and with the brightness of the atmosphere background due to scattered light and with the conditions of visibility as functions of the two previous quantities.
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Societies and Academies. Nature 132, 110–112 (1933). https://doi.org/10.1038/132110a0
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DOI: https://doi.org/10.1038/132110a0