W. R. Maxwell
Introduction: The fact that certain pyrotechnic compositions when pressed into a tube and ignited burn with a loud whistling noise has been known and used by firework manufacturers for many years. The two compositions most widely employed appear to be (a) a mixture of dry powdered potassium picrate and potassium nitrate in the proportions of about 60/40 and (b) a mixture of powdered gallic acid and potassium chlorate in the proportions 25/75. Whistling compositions have occasionally been used for military purposes. Thus in World War II the Germans had a whistling cartridge (pfeif-patrone) for signaling and the Canadians used a whistling thunderflash for training purposes. In October, 1943, the author was instructed to investigate in collaboration with the Admiralty the use of pyrotechnic whistles burning under water as a possible counter measure to the acoustic homing torpedo then being used by the Germans. As little was known about the factors influencing the intensity and frequency of the sound made by pyrotechnic whistles or their mode of action an investigation into this subject was made and is described in the present paper. A number of measurements were also made on pyrotechnic whistles burning under water, but as they are mainly of acoustical interest only, they will be dealt with very briefly.
Ref: JPyro, Issue 4, 1996, pp37-46
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