Yes! Mine does exactly that and it's extremely annoying! I hadn't noticed until today. I started running CM10 as of last night, but that might be a coincidence. Are you still using stock ROM?
I had to use stock rom yesterday so I tested charging with the phone off and there was no strange buzzing. I didn't get an indicator light, rather the scree itself stayed on with a battery charging graphic. Regardless, I'm pretty confident that the buzzing when charging with the phone off is symptomatic of this early version of CM10