Beneath the carpets you have an under felt that acts as a soundproof insulation of the car, should that get wet as you say, that is the course of your problem, water is either running from the under bonnet front of your car due to a blockage of the drain holes beneath the bonnet forward in the well below the windscreen, check that the drain holes are clear, if its only the Passenger side, the problem is there, is the door seal in good order? if the carpet is still wet, draw it out with a wet & dry vac.