Renovating an Existing Cabin space to a mixing space

[tomavon]

Hi, we are in the process of renovating our home studio space. It’s will be used for mixing predominately but we also occasionally record some acoustic guitars and DI’d instruments, so nothing loud. I’ve done some measurements over my last couple of mix sessions and don’t tend to go over 90dBA (I have a TENMA SPL meter, but I don’t pretend to be an expert in using it so will do my best to provide measurements where helpful). I’ve read the FAQs and appreciate whatever help I can get with project.

The space is a self build Scandinavian cabin type build (pictures attached), originally we built one and subsequently added a second and created a hole between the two. The other cabin is used as a workshop space as we have an electronics manufacturing company that we run from home. The goal of the project is to increase the soundproofing to intrude a bit less on the neighbours, setting a pink noise of 85dBA, I get a level of ~42dBA at a distance which would be on a neighbours property. I’d like to get this to around 35dBA if possible as when I drop the levels inside the building and measure this outside it seems pretty reasonable. If you think this is an odd choice I’d listen to it! We have good neighbours and they have no issue with the current level of sound that we produce but it would be nice to know if I were mixing later into the night that we’re not overly disturbing them. Another goal of the project is to turn the space into a better studio, rather than a multipurpose room as it has been.

The construction of the building is from pine boards that are 45mm with a hardwood floor that is raised from a concrete slab with beams resting on masonry tiles. The ceiling is vaulted and the roof is boarded with slate sitting on top and there’s a skylight in place. Dimensions are given in the (very) basic sketch up model.

Our budget is £2-3k, however if it’s felt that we could achieve much more for another £1k then it would mean delaying or extending the work over more time but we could manage it. I’m hoping that the end result will be a really enjoyable space to work in.

So here are my questions, again I apologise if they are overly simplistic, I’ve read a fair amount and have found this forum to be a great resource but this is my first venture into doing this.

1. Our intention is to insulate the ceiling between the purlins, we did this in the other cabin and found it to be good for heat and sound insulation. I then intended board and cover with tongue and groove board, this would be consistent with the construction and I think the sound in the space currently is pleasant and always attributed that to the grooved wooden walls and ceiling, but that could be an ignorant statement on my part. I’ve attached a current frequency response that I created with Room EQ Wizard. Created with the Adam S3X-V and Tenma SPL meter again. Is this a reasonable idea? And if so we will not be insulating the space where the skylight is, is this going to cause a stereo imbalance and what can we do to overcome this?

2. For the walls I’d intended on building a stud frame and insulating with Rockwell, then plasterboard, plywood and topped again with tongue and groove boards. What are the thoughts on this?

3. On the wall furthest away from the neighbours there is a window, I was going to frame this and then cover with perspex, but I could just frame it if there’s not much benefit to the perspex?

4. On the back wall I wanted to construct a soft fold out bench that was attached to the wall, my thoughts were that this would act as a mirror point for my monitoring and give a bit more seating if I had guests. Also my understanding is that the need for sound treatment here would be only in reducing reflections as I’m allowing sound to travel to the second cabin which would act as a bass trap to some degree.

5. I’m a bit unclear as to what to do with the front wall, it has a set of double doors that open out onto fields which look great and is really nice position to work in. Potentially build some soft fabric dampening here.

If I’m missing anything or have been vague, please prompt and I’ll do my best to answer.

[Soundman2020]

Hi there "tomavon", and Welcome!

I’ve done some measurements over my last couple of mix sessions and don’t tend to go over 90dBA (I have a TENMA SPL meter, but I don’t pretend to be an expert in using it so will do my best to provide measurements where helpful).

You should do all your measurements with "C" weighting, not "A". "C" is more suitable to the way we perceive loud sounds, "A" is more suitably for the way we perceive quiet sounds. It does not take into account the lower end of the spectrum so much. Use "C".

The goal of the project is to increase the soundproofing to intrude a bit less on the neighbours, setting a pink noise of 85dBA, I get a level of ~42dBA at a distance which would be on a neighbours property.

Pink noise is not a good way of for making ambient measurements, since pink noise is pretty much the same as ambient sound anyway! Rather, play typical full range music at about 90 dBC in your room, and measure that at your property line, also dBC.

with a hardwood floor that is raised from a concrete slab with beams resting on masonry tiles.

That's will likely be a problem. That floor is basically a drum head stretched over a resonant cavity...

1. Our intention is to insulate the ceiling between the purlins, we did this in the other cabin and found it to be good for heat and sound insulation.

Insulation does not stop sound. It's great for treating the acoustics within a room, but does practically nothing by itself to prevent sound form getting in / out.

Many people find this hard to understand. but there's a simple analogy: if you spill water some place you didn't want it in your kitchen or bathroom, then a sponge is a great way of mopping that up. but if you take that same sponge and hold it across the end of your tap, it does nothing at all to stop the water running through.

Acoustic absorption works exactly like that sponge: it's great for "mopping up" sound that "splashed" some place you didn't want it, but no use at all for stopping sound getting out.

I then intended board and cover with tongue and groove board,

That would be a lot more effective! Wood has mass (weight). Mass is what you need to stop sound. the more mass you use, the more sound you stop.

However, there's another factor that you are not considering: if you attach wood (or drywall) to one side of studs or joists, and you have wood on the other side too, then the joists or studs are really good at transmitting the vibrations picked up by the wood on the inside, directly though to the outside, causing the outside wood to vibrate and act as a speaker...

In order to greatly increase the isolation, you need to "decouple" the wood on one side form the wood on the other side. There are several ways of doing that, and the one you use depends on how much isolation you need.

And if so we will not be insulating the space where the skylight is,

Then you won't have any isolation!

Isolation is only as good as the weakest part. That skylight is the weakest part...

2. For the walls I’d intended on building a stud frame and insulating with Rockwell, then plasterboard, plywood and topped again with tongue and groove boards. What are the thoughts on this?

Assuming that the new "inner leaf" wall is fully decoupled form the existing "outer leaf" walls, and assuming that the floor can withstand the huge additional weight load, then yes, that would help a bit. But the overall isolation will still only be as good as the weakest parts, which will be the skylight, and the floor. Plus the doors and windows, of course, and also the HVAC system.

3. On the wall furthest away from the neighbours there is a window, I was going to frame this and then cover with perspex, but I could just frame it if there’s not much benefit to the perspex?

Glass, not perspex. There isn't much mass in perspex!

4. On the back wall I wanted to construct a soft fold out bench that was attached to the wall, my thoughts were that this would act as a mirror point for my monitoring and give a bit more seating if I had guests. Also my understanding is that the need for sound treatment here would be only in reducing reflections as I’m allowing sound to travel to the second cabin which would act as a bass trap to some degree.

If you don't isolate the second cabin in the same way as the first, then the second cabin is your weakest link...

You WILL need acoustic treatment. Lots of it. The room is very small, and the modal issues will therefore be massive. You will need substantial bass trapping. The modal issues are a direct result of the dimensions of the room, so having another cabin next to yours is irrelevant, since that does nothing to change the room dimensions.

5. I’m a bit unclear as to what to do with the front wall, it has a set of double doors that open out onto fields which look great and is really nice position to work in. Potentially build some soft fabric dampening here.

Once again, soft porous absorbers do nothing at all to stop sound. So that would accomplish nothing. That wall has to be isolated in the same way as the other three walls, and the ceiling.

Isolating a room is exactly the same as building an aquarium. You cannot make an aquarium that hods water by putting glass on only two sides, soft fabric on the third side, and leaving the fourth side open...

That is exactly what you are proposing to do with your place. Just as the unfinished aquarium will not hold water at all, so to your room will not "hold sound".

You need to isolate all six sides of your room, just like you need glass on all six sides of an aquarium.


- Stuart -