Time Machine

I set up my computer to do backups using Apple's Time Machine a while ago. The good news is that it appears to be working just fine. The bad news is it seems to fire up my external USB drive far more than I would like, especially during the evenings. Since my iMac is right in my bedroom, the spinning, chugging drive doesn't make my sleep situation any better. If I can't find a way to dial down how often it does a backup, I might have to look at getting a quieter drive.