Get a couple of metal coat hangers, cut at one lower corner, and about 4" up the opposite angle to give a bent L shape, and the bend to 90degrees. Get a couple of straws, and cut 4" off to provide handles, and you've got yourself a pair of divining rods. Hold them in your hands about 9" apart so they tip ever so slightly forward, and then take a deep breath, breath out slowly and then ask the rods to move when you cross the pipe, then ask to point in the direction of the leak, and then ask them to show tell you when you are over the leak. If you fix in your mind the type of reaction you expect (rods cross towards the centre) when you hit the water pipe (with the leak) then you'll ignore other pipes nearby.
It will take you a few goes to get the nack of it, and you can just practice finding the pipes to start with, so you don't knock your confidence, then once you find the leaks using the rods, use the listner to verify what you've found. You'll soon reach a point where you have the confidence to dig without using the listener, but even if you never do, you'll find the rods help you locate the general area quicker than you normally would.