Not sure if this was posted before but seems MIT did a comparison on vibrations of frame based on materials http://web.mit.edu/2.tha/www/ppt/Bike-ISEA.pdf

Seems AL transmits more vibrations than carbon and steel transmits the least. The reverse is that more energy is needed to speed up riding steel and AL requires the least energy. Interesting as i see in other posts that frame material makes little difference and is only marketing gimmick