Sine pulse on a shaker

The "Haversine" adds a 1/2 cycle before and after the test pulse so that the entire time history will integrate to zero velocity and zero displacement. The shaker armature has to end up back where it started and "parked" (no residual velocity). These additional 1/2 cycles are usually at very low frequency and much lower g than the test pulse. This is assumed to be non-degrading to the test article. If looked at in the SRS, they have little or no effect. Drop shock machines may produce a single 1/2 sine, but the shape is rarely a real 1/2 sine.