In ultrasonic processing, it has been a practice to measure intensity of ultrasonics as a product of plate current and voltage as indicated on ultra sonic generator. At low frequencies the standard equipment is available, such as the sound level meter, to measure the absolute intensity, but at higher frequencies the problem becomes complicated by the diffraction effects on account of the size of the measuring device. In this investigation an attempt has been made to construct a measuring device (called the probe) to measure intensity. A small barium titanate cylindrical element (1/16 inch in diameter and 1/16 inch length) was used as a detector-convertor of sonic pressures. The alternating voltages thus produced were indicated by a vacuum tube voltmeter. This element was cemented in a hypodermic needle in turn was held in a lucite rod (1/2 inch in diameter and five inches in length) which served as a holder. This arrangement was used to probe the sonic fields of cylindrical and bowl shaped transducers. / Ph. D.