Interior doors of the type frequently used in rented housing (I'm speaking in particular of apartments) seem to be hollow and do not do a very good job of sound insulation. If for example a laundry room was behind the doors a great deal of the sound from the laundry room would be transmitted to the rest of the apartment.
In which ways could one (price-efficiently) insulate these doors, such that sound transmissions would lessened?
Best Answer
A sound blanket on the laundy side would be simple. See my answer here
Drilling and foaming the door with low expansion, door and window polyurethane foam. The trick will be figuring out where the cardboard internal baffles go. I would fill a horizontal row of 3 holes equally spaced, every foot. Allow some time between fillings to let foam setup. (but not so long for the nozzle to clog (10 min?)