It’s high time we said a few more words about acoustic doors …

So here we go! We’ve written several articles in the past on acoustic doors – sometimes called soundproof doors – and we’ve covered a wide variety of topics, ranging from what sound actually is and how it’s transmitted; how the volume of noise is measured and comparisons made; how to achieve noise reduction in principle; and what are the maximum noise levels permitted (legally) in different workspaces and environments.

We thought that this time that we would provide a brief refresh on certain topics, just to remind you. First up, what do they do?

What is the purpose of an acoustic door?

Essentially, they perform two functions:

act as a sound barrier to reduce noise levels entering and leaving an environment or workspace
because of their necessarily solid construction, it is probable that the doors will also provide some protection against the spread of fire and smoke

We might often think about acoustic doors providing a barrier to noise getting in, such as in a recording studio, but let’s not forget that equally importantly there are rooms and environments where it’s important not to let noise get out – good examples are interview rooms, board rooms, and, at the other end of the noise scale, concert halls.

Where are acoustic doors used and why?

There are many environments where we would want the doors to provide effective sound-proofing – whether it’s partial (some noise getting in or out is acceptable) or total (no sound should be able to get in, or out, or both). Let’s look at some obvious examples across the range:

Total

recording studios
police interview rooms
operating theatres

As close to total as it’s practical to get

music halls and concert venues
libraries
museums
galleries
interview rooms
board rooms

Try and keep noise to a minimum

airports (from the outside in of course!)
hospitals and nursing homes
hotels
offices
educational establishments

Recommended noise levels

Below are recommended maximum noise levels for a variety of workspaces:

Workspace	Recommended maximum noise level (dB)
Offices	40 – 45 dB
Large Offices	45 – 50 dB
Classrooms	40 dB
Large Lecture Rooms	35 dB
Music Room	30 dB

Here are some sound reduction guidelines:

20 dB	Normal speech will be readily audible
25 dB	Loud speech will be clearly audible
30 dB	Loud speech will be clearly audible under normal circumstances
35 dB	Loud speech will be audible but difficult to distinguish
40 dB	Loud speech will be faintly audible but cannot be distinguished
45 dB	Shouting will be audible but cannot be distinguished
50 dB	Shouting will be barely audible
55 dB	Shouting will not be audible

So how do we measure the noise reduction?

As we’ve seen before since the Decibel is a logarithmic unit, and the percentage scale is linear, a statement like “the soundproof door would reduce noise by N %” is meaningless. And to emphasise the point, the Decibel scale has no maximum value, so it’s impossible to calculate a percentage reduction anyway!

We use instead a ‘Weighted Sound Reduction Index’, Rw, which expresses the difference between the sound intensity hitting one side of a structure and the resulting sound measured on the other side, i.e. it rates the effectiveness of a soundproofing system or material. Increasing the Rw by 1 translates to a reduction of approximately 1db in noise level. Therefore, the higher the Rw the better the insulation provided by the soundproof door will be.

See our ratings for acoustic doors provided

Noise abatement and Quiet Mark

It’s not only for legal or practical reasons that soundproof doors might be required. Generally, we are subject to too much noise almost everywhere we go, and this can seriously affect the quality of our lives …

“Exposure to persistent, unwanted sound is detrimental to health, learning, productivity and quality of life”

so said John Connell, founder of the Noise Abatement Society, as long ago as 1959. And think how much louder the world has got since then!

Quiet Mark sprang from the response to public complaints received by the Noise Abatement Society’s 24/7 national noise help-line, concerning the volume of excessive noise.