fatbenelton wrote:Not ideal but a phone booth size frame filled with rock wool and covered in plasterboard would do something...surely?
True, the first principles of soundproofing are simple. To stop sound getting in or out you need to block any air gaps, (that is the one thing that will make the biggest difference). The next thing it to reduce transmission through the fabric of the room (doors, windows, floor ceiling and walls). To make a significant difference a booth needs to be decoupled from the floor, to be sealed, and to have mass in it's walls, floor and ceiling. Plasterboard will make a difference and Rockwell will reduce resonances in any voids. A duvet walled booth will make little difference to the mids and none to the low end (though voices don't have much real LF energy)
fatbenelton wrote:Even if the doorway leaked sound he's looking at attenuation/reduction not elimination. Whether you can do it for $500 Is another question but a wood frame and plasterboard isn't wildly expensive.
As you say, even a non sealed door will reduce sound leakage by a noticeable amount, particularly at the high end (easy to test, turn the radio on, walk out of the room the close the door) but it won't do much to reduce the tapping feet or any LF that is there.
The other issue is that an effective booth is going to be heavy (two or three layers of plasterboard, one inside two outside the frame, outer fixed with green glue) and domestic bedroom floors are not designed to support heavy weights (ok, maybe, if you'd seen my wife wardrobe......). Joking aside it does need to be considered.