Detecting abnormality

In apparatus for detecting a selected type of abnormality in a predetermined region comprising transmitter means for directing an elastic mechanical wave in a series of pulses to portions of the region and receiver means for providing response to the wave pulses reflected therefrom, wherein the amplitudes of pulses reflected from a portion of the region where such type of abnormality is absent (a normal portion) may approximate the amplitudes of pulses reflected from a portion where such type of abnormality is present (an abnormal portion) and thus make it difficult to distinguish between normal and abnormal portions, the improvement comprising

• in the transmitter means, mechanical wave radiating means providing an irregular cross-sectional radiation pattern,
• means for providing relative transverse repetitive motion between the radiating means and a given portion of the region while a series of pulses are directed to the same portion of the region, superimposed on any scanning movement from portion to portion of the region, to provide randomlike variations in the shapes of successive pulses where reflected from a normal portion of the region differing detectably from any variations caused in successive pulses where reflected from an abnormal portion, and
• means responsive to a plurality of successive reflected pulses for effectively superimposing them, the types of wave shapes of the superimposed pulses being indicative selectively of a normal or an abnormal portion of the region.