The measurement and numerical modelling of the diffraction field of a spherical ultrasonic transducer working in the air at the frequency of 1.3 MHz.

This paper presents the results of measurements of the acoustic diffractive field in the focal area of a spherical ultrasonic transducer working in air at a frequency of 1.3 MHz. The measurements show some differences when compared to the theoretical distribution. Computer modelling of the transducer aperture complex function and the numerical simulation of its radiation are used to explain those differences. It is shown that the wave aberration of threefold symmetry (described by the Zernicke polynomial) and the random distribution of grains in the impedance matching layer are the main causes.