ABSTRACT
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Several means of generating sound and ultrasound have been in existence for many years. Among the earliest were vocal chords, tongue, lips, and teeth. Man early learned to make whistles and whistle-like musical instruments, such as fi fes. The modern industrial use of ultrasonics is commonly related to Galton’s development of moderately high-power ultrasonic whistles, which he described in 1883. The frequency of Galton’s whistle could be varied over a wide range, from sonic to ultrasonic, by varying the distance from a nozzle to the edge against which a jet of air or other gas from the nozzle blasted.
