Initial design advise wanted

[routercnc]

Hi driftspin

Noise reduction is related to how heavy the walls are. Look up 'mass law sound reduction' for more info.

There are some basic calculations on this site:
http://www.engineeringtoolbox.com/so...ls-d_1409.html

Let's say with the cnc machine running noise levels inside the workshop are 90dB. If the surrounding urban noise levels near the workshop are 50dB (with the machine off) then you need to achieve 40dB reduction.

With concrete at 2300kg/m3 and 0.2m thick this gives surface mass of 460 kg/m2. This gives an average noise reduction of 52dB, which would be enough.

With wood at 400kg/m2 and 0.044m thick this gives surface mass of 17.6 kg/m2. This gives and average noise reduction 28dB, which is not enough on its own.

Assuming you are stuck with wood, this can be improved by adding another wall with an air gap in between. Using the air gap you get more noise reduction than if you just stuck the walls back-to-back with each other - but they must not touch each otherwise the vibration will pass easily from one to the other and the benefit is lost. So mount them on separate vertical studs. The larger the air gap the better the performance, but workshop space is lost.

Finally you can add absorption material in-between the walls which takes out the high frequencies (it does nothing for mid to low frequencies which is why you need the double wall first). This can be anything fluffy, so rock wool is fine.

Make sure you seal any gaps otherwise lots of the noise benefit is lost. Make sure the roof, door and window specs are considered as well (plus floor if it is just suspended wood).