Modeling of the electro-acoustical channel of an angle probe for a side drilled hole type reflector made it possible to calculate the forms of the run round pulse generated by the radiation of a surface Rayleigh wave propagating along a concave cylindrical cavity and the wave pulse when reflected in the geometric acoustics approximation (mirror) for different radii of the hole and to obtain estimates of the ratio of the amplitudes of these pulses and the difference in their registration time. Comparison of the experimental results with those obtained by calculation for holes with radii of 2 and 3 mm showed their quite good qualitative and satisfactory quantitative coincidence. Estimates of the radius of a cylindrical hole are given based on the experimental delay time of the run round pulse and the Rayleigh wave velocity for a flat surface using a simple ratio; the range of the ratio of the diameter of the hole to the length of the transverse wave in the medium in which such an assessment is advisable is indicated, and an example of the values of the lag time in this range is given.