... they hear noise when making an outside call? But NOT on receiving a call??? Hmmm.
BTW, I can no longer take the protestations of clients at face value. So many times, it seems, they are not connecting the dots correctly. Of course, why should they? They are not trained in these areas. But since they issue them with confidence, it causes doubt about your own troubleshooting skill.
Also, I have not have problems with noise in Nortel systems.
You checked at the D-Marc... Is the inside cable in (presuamably) good shape and not likely to have been damaged?
In summary, trust the force and your test equipment. After failing to solve a couple of noise problems I spent $600 for a SideKick meter that directly measures noise. Then you can SEE the noise level and show the client. This is much, MUCH better than judging by ear.
Or find a friend. One of the most helpful people in this business was someone I met when I was stumped and went to the Yellow Pages and called someone and told him I would pay his regular rate for "consultation." Most people will try to help someone who asks. We have been sharing work ever since.
Yours,
Mike