Not sure if it might help you in your situation, but it might help others who try to isolate noises. One easy and cheap way to help isolate noises is to use a homemade mechanics stethescope.
The two tools I use for this is a length of tubing, and a stick or rod. Use either one, whatever u happen to have around.
With the tubing, heater hose, garden hose, wrapping paper tube, etc., hold one open end to your ear, and with the other open end, use it like a microphone, sweep around the engine bay.
With the stick, dowel, rod, screwdriver, pvc pipe, anything solid, etc., you can press the one end to your ear, the other end to any hard surface that you want to listen to.
I just used this method yesterday on a friend who was worried about his engine making this loud ticking. He had a broken golfclub shaft in his trunk, and using his old golfclub shaft, I pressed it against his fuel rail, and showed him that the clicking was his Fuel injectors. I then showed him how you can listen to each individual injector, and use the "tool" in diff places all the way accross the valvecover and hear the individual valve lifters, as well as hear the exhaust flowing through the exhaust manifold, etc., etc.,
