The auditorium is a box inside the building, not a hall with absorbent paint.

The box

Isolating the house from the rest of the building means mass, or a double wall that is not tied, a lid that does not sit on the same beam as the street roof, and a floor that does not run unbroken into the foyer. A box within a box — a room on resilient joints — is used when the programme is quiet music or a reinforced show beside a hotel or another hall. It is not the assumption of every school theatre. It is the tool when the required field figure is higher than a single mass will give.

Low frequency is what exposes a weak box. A strong sound system, a kick drum, or an effect under 80 Hz. A light wall can post an acceptable Rw and fail in the lower third-octaves. A contract that stops at a single Rw, with no curve, does not catch that failure. Ask for third-octaves, especially 63 and 125 Hz, between house and foyer and between house and the next hall.

• A two-door lobby at the audience entrance raises the limit more than swapping one leaf.
• Control-room glass is an isolating element: unequal thicknesses, a wide cavity, a frame with no vent slots.
• The backstage opening is closed as an acoustic doorset, not as a curtain.

Pit and tower

The orchestra pit usually connects to corridors under the house. If those corridors reach a quiet room or a street exit, the flanking path is clearer than the wall. Close the corridor with a door, and break the floor if people walk above it. The fly tower is tall and light, so rain arrives as impact. The roof over the tower is separated from the frame, or weighted and isolated for impact, if rain is part of the programme. Winches sit on resilient bases, and their track is not tied to the house wall with a continuous steel angle.

Dressing rooms and rehearsal

A dressing room under or beside the house is heard if the slab is shared and the door is ordinary. Insulation from the house, and from the next dressing room, is a line of its own, separate from absorption in the house. A rehearsal room that runs during a show needs the higher figure, not a school-classroom figure. Inside the rehearsal room, absorption comes afterwards so a player can hear themselves. The order is the shell, then the tail.