well thats probably still true. Tip speeds get close to and sometimes through the speed of sound - boeing stearmans make the rasping noise they do because of the tips going supersonic. A 90" prop on something like a king air is describing a path about 7 metres round and at 2200 rpm thats ..um M0.78.
Saturday afternoon maths of course..
Do you mean just rpm? if so, no idea, google is your friend
http://www.enhanced.aero/pdf/performance_raisbeck.pdf
(might be talking rubbish.. am sitting here watching the F1)