Noise transfer thru wall can be greatly reduced fairly inexpensively.If the wall is not sound proofed the sheetrock is ripped off the shared wall and all the stud bays are filled with regular r-13 insulation. Then a layer of soundboard goes up covered with drywall. The sound dampening is amazing. There are more high tech products but this works pretty well.
$4-$5 per sqft of wall by handy man, materials and labor+painting.
