4WD Dyno Cell Construction Blog.
(Part 2... The decibel challenge)
The Decibel challenge.
As most of you will know, dynos create huge amounts of noise and sadly our new unit has 2 directly attached neighbours, neither of whom we want to be upset or complaining about us. We had to figure out how best to stop transmission of noise and vibration to the surrounding units. After much research, umming, ahhing and head scratching, I finally settled on the following system.
- Wooden stud walls.
- Acoustic grade rock-wool.
- Genie clips.
- Resilient bars.
- 2 layers of 15mm Acoustic grade drywall.
- 4mm accoustiblock sound absorption mat in between the drywall layers.
- Acoustic grade sealant at every joint, so no panel or wall touches any other one directly.
- Acoustic grade tiling to finish the walls aesthetically and control nasty reverberance.
This is an interesting system that's normally used to assemble cinemas and recording studios etc and it uses a special vibration damping clip to secure a furring bar to a wooden stud in such a way as to decouple the boards away from their mounting studs. It is a lot harder to explain than to show you, so here is a picture or two.
First, the whole cell is lined with acoustic grade rock-wool.
The tiny ceiling space was no fun to do. (So im told... LOL)
The genie clips are then installed. These screw to the wooden studs...
The furring bars mount onto these clips, giving you a mounting system that isolates the wall panels from the framework with a little sound dampening unit, not unlike an engine mount, and doing the same job.
The first layer of acoustic grade 15mm plasterboard is then mounted to the furring bar.
Once the wall is built in this fashion, it is then covered in rolls of this stuff which is a special sound deadening material which allegedly, is denser than lead. Its about the same weight too, it takes two large men to carry a roll and its impossible to hold a full roll in place on a wall without three of us.
And then a 2nd layer of 15mm acoustic plasterboard is fitted on top of it, to make an ultra dense sound absorbing sandwich. All joints are sealed with acoustic sealant.
The next image shows the soundproof sandwich. Remember, this is also mounted to the sound damper and then to be covered in acoustic foam. There wont be much sound getting past this!
This was an absolute headache of a job and took up the lions share of the work. However, it was absolutely necessary to ensure we suppress not only noise, but ensure an airtight room that will flow air the way we want it to, and not allow fumes to seep into adjoining office spaces (Or sound!).
The next issue was soundproofing the viewing and reception area whilst maintaining the window for customers to watch. This path led to me securing a customer made triple laminated acoustic grade window.
The final touch is to install acoustic grade foam over every surface to dampen nasty harmonics, add that final layer of soundproofing and provide nice aesthetics. I really like the way it looks, which is handy, as it meant no pointing too!
With that job nailed off, the unit is finally starting to look how I envisaged it from the start. It really is starting to look like a dyno cell! However - we also need to extract the exhaust gas and its associated noise as quietly and efficiently as possible. Now this really can be a headache, especially with high power diesel vehicles, so we got the specialists in to spec this system for us and agreed a pretty rare deal... If we can measure any exhaust gas in the cell while the dyno is running, we don't pay a penny until its fixed by them at their cost. You cant say better than that I reckon, but as with everything in life, it comes at a price... a big price.