The transducer is located at the crossing between the dashed lines. The dashed lines represent left and right element surface. The shaded areas represent the distribution and intensity of sound transmitted from the left and right SI beams (starting at the crossing). Quite alot of sound is sent towards the surface. I have tried to draw a 3D figure, but these cases are so extreme that my program can't do that due to too low decimal resolution.

(There is wide sector right under the transducer where left and right beam overlap. The large distance between left and right element array (about two inches) causes a phase shift between the beams and therefore also a complicated interference issue. The "fingers" pointing downwards indicate this interference. This is the reason why the DI from SI technique is doomed to be inferior to dedicated DI.

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