A door is a set, not a leaf. The threshold and the frame are the insulation.

What is bought

An acoustic doorset includes the leaf, the frame, hinges that do not twist the seal, the threshold, and a drop seal or floor gasket. The figure printed on a laboratory leaf assumes a closed perimeter gap. On site, a millimetre under the leaf brings speech back. A vision panel in a classroom door — if safety requires one — is rated glass of the required thickness, not an opening covered with ordinary glazing.

• A solid door with no seals: a rough order of Rw 20–27.
• A well-fitted set: often 37–45, and higher only with a lobby or a pair of leaves.
• Do not average the wall Rw with the door Rw. The opening follows the weaker element once its area is not trivial.

The lobby

Between a theatre foyer and the house, or a school corridor and a music room, two doors in series with absorption in the space between them raise the insulation more than swapping a single leaf for a heavier model. The brief should say the two doors are not open together during the sensitive hour. An escape door in an operable wall is part of the insulation and is tested with the wall, not exempted from it.

Handover

On the measurement day the doors are closed as in operation, not taped shut for the test. If the figure falls short, the repair is the seal, the threshold and the frame before the wall is rebuilt. Write in the line: a doorset, a field or laboratory figure, and the measurement standard.