I had the same problem, and so have others, with the Aztech modem. Call or email Dell tech support, describing the problem. They will suggest a series of tests to isolate the problem. Do the tests, and be as informative and specific as you can about the results. If the modem flunks, you should get a new one. They replaced mine with a 3Com which doesn't hum.

I have been battling with Pac Bell over a humm that sometimes is non-existent, sometimes overwhelmingly loud so that I can't talk. I am making such good progress that now after they missed 4 appointments I don't even get a dial tone. I have DSL, do you? I wonder if that is a factor?
Drew

To dperkins.

Good luck with Pac Bell. We also had an ongoing issue with a loud humm on one of our lines. It turned out that PG&E had a power line problem that was causing the inductance on a whole bunch of phone line. Try getting both PG&E and Pac Bell to admit a problem and then solve it!

Thanks to M. Currie regarding the problem with the Aztech modem and phone line hum. My Aztech was also replaced with the 3Com and the problem was gone!!