Does a flat ceiling provide the best sound?

I have heard that flat ceilings in homes are superior than a peaked ceiling for acoustics.  Is this because there is less space for sound waves to develop and reflect back down?  I'm thinking of the more shallow peak of a four-season addition that is fairly low and simply follows the roof line, not so much the steeper vaulted ceilings in living room/dining room/kitchen floor plans.  Would some rug hangings or similar help correct this in a shallower peak?  Thanks!