My modem has the moans and groans help!

My Gateway modem has this weird sounding moan. It sounds like a dog snoring or grawling...every few seconds.
I'll type it as it sounds

ggggg ggggggggg ggggggggg ggg ggggggggg gg gggggg ggggg gggggggggg ggggggg ggggg

It just started this a/m. It hasn't been that long since the fan was cleaned, and I even blew it out again just now. No change though,
Anyone know what could cause this noise?? Its driving me nuts!!!

Over all the computer itself seems to be working fine. Just the noise!