well met fig6 illustrates an example of an intensity field of the same c4 2 transducer when it is focused at 30 mm instead of the 50 mm in fig5 it can be seen that the force distribution in this example is not a line force rather the max intensity splits into two separate peaks symmetric and away from the center plane of the transducer the c4 2 transducer uses an acoustic lens to provide a fixed elevational focus at about 70 mm away from the transducer surface this leads to poorly focusing in the elevation direction when the beam is focused too close to the transducer as shown in fig6 the force field of fig6 can be simplified to two line forces as illustrated in fig7 to illustrate the bias on shear wave speed measurements fig7 shows the two line forces in a focal plane perpendicular to the axis of the transducer that is in an out of plane slice at the focus depth d f such as the one shown in fig1 the rectangular broken line box 702 represents transducer with its ultrasound beam directed into the image plane the line forces are also directed into the image plane and therefore are represented by two dots source one 704 and source two 706 shear wave speed.