Security guards do keep a close eye on the building especially to monitor noise levels during quiet hours.  However, you will hear people coming and going from early morning or night skiing and typically they are wearing ski boots.  Since it is pretty hard to tip-toe in ski boots, you may want to bring a pair of earplugs along with you. Also, if your unit is slope-facing, there may be some noise from the groomers working their magic at night (Winter only). Again, you may want to bring a pair of ear plugs along with you if you are a light sleeper. Personally, I never travel without them!