Myth: Put a hole in the wall to let the noise out

Fact: Sound isn’t a wild animal waiting to escape

It is occasionally suggested that if an opening is formed in a plant room wall facing away from the noise-sensitive location, this will reduce the sound level reaching the area to be protected.

In reality, sound reaching the receptor will be a combination of direct (not reflected) energy that is unaffected by the presence or absence of a reflective surface behind the noise source, and reverberant sounds that have been reflected from one or more surfaces before leaving the plant room. The reverberant sound level will be reduced if the area of openings in the plant room is increased, but this is only by 3dB for every doubling of absorptive area, which is a noticeable difference, and will be limited by the level of direct sound.

The overall effect will usually be a negligible difference in the sound level from the original aperture, and additional sound egressing from the other opening, which may compromise any reduction to other areas that would otherwise be achieved.

Lining an Enclosure or Plant Room may help to reduce the noise level slightly, but is also the subject of another Myth Buster.