Acoustical control. Walls, partitions and floor-ceiling constructions separating dwelling units from each other or from halls, corridors or stairs shall have a minimum sound-transmission class (STC) rating of 45 and a minimum impact noise rating (INR) of minus five. Where practical, each apartment or townhouse shall be separated from adjacent apartments or townhouses by other than living spaces, such as bathrooms, kitchens, closets, stairs or mechanical areas. Penetrations or openings in walls, partitions or floors shall be packed, sealed, lined, back-plastered or otherwise isolated by sufficient mass to maintain the required STC ratings.