Russian sonars are seriously flawed in the game. But US should work quite well. Don't forget all sonar conditions affect active as well, especially SSP and sea state.
Getting ping not sooner then at 3000 yds sounds to me like cross-layer ping. Layer always blocks sound completely in DW, but when you get closer, the effect disappears.
Here is my older post about DW sound propagation model.
http://www.subsim.com/radioroom/showthread.php?t=117814
So let us know about your depth, target depth, sea state, and SSP.