Actually, you're right. I work at Owon where this scope was designed, and I can't hear my Rigol over the sound of all the engineers hitting their heads on their desks to get warmed up. Then they start their hourly ritual crying, and dear lord I can't hear anything over that.
Seriously, though, is there some variation in fan loudness in the DS1000 series that I don't know about? Mine's quite quiet. I wish I had a way to measure it, but it's really one of the quieter cooling fans out there.