Q: when it stops buzzing then everything works fine.
A: Are you sure it's your modem, or are you talking about the processor? Edit: Ok, I just talked to someone else for clarification. By modem you may be referring to the actual computer. If there is a little green light on it that flashes when it is making the humming sound then that is just your computer precessing what you want it to do. It's perfectly normal unless it seems to take a inconveniencing long time. If that's the case you may need a new/faster processor or more ram.