I'm *assuming* (I know, bad idea) that he's looking for ambient SPL levels...
You need a SPL meter. Generally, you're looking for a "C-Weighted / Slow" reading (as opposed to "A" weighted or "fast").
Don't know if you Radio Shacks out there, but I hate to say that thiers is the best budget-minded unit I've used in a long time. The new <$100 units at MF/GC are absolute junk (IMO/E).