Ok, so I have 6 lights in my garage. Two are driving me nuts with the buzzing. 
4 are 2 T8 bulbs with a blank unmarked white ballast that is fairly small, they don't make any noise at all.
The other two are 4 bulb T8 lights and they buzz. Drives me crazy. The ballast looks like regular ballasts from my days with T12 bulbs, but it is marked clearly for T8 bulbs.
Any ideas on what the difference is?
Here is a pic of the buzzing ballasts:
While two of the 2 bulb lights are brand new, the other two are the same age as the 4 bulb lights. So I don't think its an age thing, maybe just a crappy light or something like that?

4 are 2 T8 bulbs with a blank unmarked white ballast that is fairly small, they don't make any noise at all.
The other two are 4 bulb T8 lights and they buzz. Drives me crazy. The ballast looks like regular ballasts from my days with T12 bulbs, but it is marked clearly for T8 bulbs.
Any ideas on what the difference is?

Here is a pic of the buzzing ballasts:
While two of the 2 bulb lights are brand new, the other two are the same age as the 4 bulb lights. So I don't think its an age thing, maybe just a crappy light or something like that?