Soundproof & Acoustic Doors

A complete assembly designed to stop sound: a heavy, layered leaf, a frame that seals against it on all four sides, perimeter gasketing, and an automatic drop seal at the bottom. Its performance is quoted as an STC rating from a laboratory test of the whole assembly. The individual parts matter less than the fact that they were tested together — which is why an "acoustic door" bought as a leaf alone rarely delivers what the brochure said.

Sound Transmission Class — a single number summarising how much airborne sound an assembly stops across speech frequencies. Higher is better, and the scale is not linear: normal speech is generally unintelligible through STC 45 and inaudible through about STC 50, while a standard commercial door with no seals lands somewhere in the twenties. Every additional few points costs noticeably more than the last.

It depends what is on the other side. Roughly: STC 30–35 for ordinary office privacy, 40–45 for meeting and board rooms and hotel guest rooms, 45–50 where confidentiality is a requirement — HR, clinical consultation, legal — and 50 plus for studios, music rooms and mechanical spaces. We would rather ask what you are trying not to hear than sell a number.

You can improve it, and sometimes that is enough. Fitting proper perimeter seals, an automatic drop seal and a sealed threshold to a solid-core door typically gains several STC points and costs a fraction of a new assembly — and it fixes the commonest problem, which is that the sound is going under the door rather than through it. What retrofitting cannot do is turn a hollow-core or lightweight leaf into a rated acoustic assembly.

Almost always a gap. The three usual culprits are an undercut at the bottom with no drop seal, a threshold that was left off, and a frame that was not part of the acoustic assembly. After that come flanking paths — sound going over the wall through an open plenum, through shared ductwork, or around a partition that stops at the ceiling tile. A door cannot fix a wall that does not reach the deck.

Yes, and in hotels, hospitals and offices it usually must be. The rating comes from the core and edges, the sound from mass and seals, and assemblies are listed for both together. What is not permitted is adding gasketing or a drop seal to a labelled fire door on site and assuming the label survives — the combination has to be specified and listed from the start.

Both work; the room decides. Steel assemblies reach the higher ratings and belong in mechanical rooms, plant, studios and back-of-house. Wood assemblies suit finished space — meeting rooms, hotel suites, clinical and office interiors — and reach the ratings most of those rooms need. Where the door also has to look like the millwork, wood is generally the answer.

An acoustic door can take up to 8–12 weeks to produce and to source the hardware. Then 1–2 weeks to schedule the job and install it, depending on the size of the project. These are engineered assemblies rather than stock items — the leaf, frame and seal set are ordered as a set, and substituting any part of it changes the rating. Hanging one acoustic door and frame is usually a day on site; a studio or school fit-out with many openings runs over several weeks.