The same noise is not present with smaller bits. There is a very aggressive noise around 90 with the 1/2". We generally run 1/4" bits, and hadn't had to use it in months. Last time it was used it sounded fine, however there have been plunge mistakes since then (nothing within the month or so). When i changed the bit and collet to the 1/2" it was immediately evident that it was not right. The whole moving arm vibrates and shakes.
Noise is the same at all z heights, changes based on x/y coordinates a little.