Diffraction phenomena usually take place as the wave pass around kinds of sharp angular elements, such as point, corner, edge, wedge, etc. As the focused probe beam of a lens spherical cavity interacts with the sharp edge of an element, the diffracted signals arise in various time delays. A signal aberration is observed in ultrasound echo signal pattern (A-(O)-scan), with a combined formation - a main pulse signal reflected from the interface (surface) of specimen, attached by an additional pulse signal reflected from the edge of this specimen; the edge diffraction impacts on 2D acoustical imaging (B- and C-scan image); The paper presents the recent experimental investigation, revealing that the edge diffraction participates in the construction of 3D acoustical imaging. An upward or downward bowl-shaped outer-rim, encircle the edge of an internal structure, with a virtual enlarged size in full direction, or an arced slot-rim around the front surface of the specimen. Therefore, edge diffraction impacts should be taken into account for acoustical imaging in the field of NDT/E evaluation.