How the detectability of small flaws is related to the ultrasonic wavelength

In the early 1970s, we developed SARD-1, an ultrasonic apparatus for the automatic detection and estimation of flaws [1] under the supervision by V. V. Zalesskii, head of laboratory of acoustic methods at Rostov State University. The distinguishing feature of its design was the presence of dedicated units for statistical processing of detected signals with a view to identifying a flaw and estimating its parameters.