Thanks to all for the cool information!
I'm very sorry to be so late in responding to your question. Yes; there is a way to get rid of the "hum" in the background. Cool Edit has the ability to "wipe out" any HISS or background hum - but this software is really expensive- Audacity does pretty much the same thing; but it's FREE; at least, the last time I looked- it was free. You can find it listed in the TOOLS section at www.videohelp.com
I think there's a "How To Use Audacity"
giude there as well.
That "hum" is called a "GROUND LOOP HUM"; this drives me crazy whenever that hum happens; but Cool Edit takes care of the hum fairly well.