Measurements of the Second‐Harmonic Component of a Plane, Finite‐Amplitude Wave

A method for the measurement of the second‐harmonic component of a plane, finite‐amplitude wave as a function of the distance has been devised that makes use of fixed‐distance measurements in a two‐transducer pulsed system. The fixed‐distance method eliminates problems of transducer alignment and traversal. The technique is similar to a method previously used for obtaining the fundamental‐frequency component as a function of the distance from fixed‐distance measurements [J. Acoust. Soc. Am. 34, 1991(A) (1962)]. Measurements have been made in water at 5 mc/sec at distances up to 80 cm, and are compared with theory [J. Acoust. Soc. Am. 33, 1196 (1961)] over a range of the initial‐value parameter αL. Optical methods are used to calibrate the sending transducer and to measure the harmonic content of a known wave, which allows one to calibrate a tuned receiving transducer. [This work was supported by the U. S. Office of Naval Research.]