Acoustic enclosures: mass on the outside, absorption inside

Most noise complaints from plant rooms are solved by the same principle. Why density alone will not fix it, and where MLV barrier earns its cost.

Two different jobs

Blocking noise and absorbing noise are separate functions and need separate materials. Mass — sheet steel, MLV barrier, dense board — blocks transmission. Porous material — density-graded wool, open-cell sheet — absorbs energy inside the enclosure so it does not simply build up.

An enclosure built only from wool leaks noise. An enclosure built only from steel resonates. Both together is the answer.

Where enclosures leak

Almost always at the openings: ventilation gaps, cable and pipe penetrations, access doors without seals, and the gap under a panel. A single unsealed penetration can undo the rating of an entire enclosure, which is why we detail attenuated ventilation paths rather than plain holes.

Measure before and after

We take a baseline reading at the boundary or the operator position, design to a target, and read it again on handover. Without both numbers, an acoustic job is a matter of opinion.

If you would like this applied to your own plant rather than discussed in general terms, send us the details and we will put a specification in writing.