Attic Shaped Studio

[garethmetcalf]

Wowsers, what a load of effort for something totally hidden from view. This is how I've felt many times!

Congrats.

[endorka]

Source of the post Wowsers, what a load of effort for something totally hidden from view. This is how I've felt many times!

It's all part of the charm isn't it!

More work until the wee small hours again last night & this morning. The noggin under the silencer added a huge amount of stability. It also allowed the silencer to be attached to it with screws perpendicular to the OSB as well as into the edges.

Lower part filled with pink fluffy insulation.

Lower part of the wall added, top part filled with insulation.

Upper part of the face added.

[endorka]

I've been adding several skim coats of plaster to the builtin bass traps at the back of the room. It's taken several days as plastering is new to me. There are 18 external corners and a long 40° internal corner to finish to a presentable standard. Not the ideal subject to learn on but in for a penny in for a pound! This was the first coat, it was well rough, I've done a couple since then and it's almost there now.

I put the plasterboard on to the left hand knee wall. Most of these cables are now in place so I had to cut the cable run holes before attaching it. Fortunately they lined up pretty well. Because I had to put the cables through the holes one by one, I had to apply the green glue once they were all through. Very messy and has to be done in 15 minutes or less, thus the fingerprints all over the board

I cut the large square hole for the ventilation after attaching the board. It's rough, but won't be visible so not the end of the world. I'll figure out a way to make the faces smoother to reduce air turbulence. The red stuff sealing the cables is from putty pads. I prefer using this to caulk as it is easier to build up a deep layer and can easily be removed & replaced if required.

I did a couple of quick ear tests of sound transmission to the room below the builtin bass traps. First was running a floor standing fan at the back of the studio. Before any of the sound isolation improvements in this thread, the sound audible in the room below was loud enough to make you think the fan was in there, not the room above. The new double layered bass traps built in to the rear wall combined with previous incremental improvements have rendered it virtually inaudible. Quieter than ambient room noise; I had to get close to the ceiling right under it and really listen to perceive a slight thrum.

The other test was a reference track, Peter Frampton's "Show Me The Way". It's useful as it has a very dynamic kick drum & bass guitar that cuts through boundaries like butter. With the old rear wall - one layer of 12.5mm plasterboard, probably 9 kg/m2 surface density, track playing at standard monitor level in the room above, the doof doof of the kick and and bass was very prominent. With the builtin traps, double layer of OSB & 15mm acoustic plasterboard + green glue, surface density around 25kg / m2, there has been a huge reduction in transmission of low frequencies. It really is quite remarkable.

There's a little oddity though. What remains of the sound is predominantly midrange. But I think I have an explanation. If I stick my head in one of those builtin bass traps and talk, the flutter echo causes some midrange frequencies to resonate in the chamber. I reckon these are the same frequencies getting through to the room below. If this hypothesis is correct, stuffing these traps with insulation should reduce the resonance inside them, and hopefully also to the room below.

Cheers!
Jennifer

[SoWhat]

The other test was a reference track, Peter Frampton's "Show Me The Way".

Studio version or the now-classic version from "Frampton Comes Alive"????

[Starlight]

Source of the postI'll figure out a way to make the faces smoother to reduce air turbulence.

Just tossing out an idea: If you face the bare plaster and OSB ends with strips of wood (almost veneer thin as I guess you don't want to make the hole smaller) the same depth as the OSB and plasterboard combined, that should give you a smooth, paintable face.

[endorka]

Just tossing out an idea: If you face the bare plaster and OSB ends with strips of wood (almost veneer thin as I guess you don't want to make the hole smaller) the same depth as the OSB and plasterboard combined, that should give you a smooth, paintable face.

That is an excellent idea thank you. I have some 6mm thick stripwood offcuts from the riser build, they should do the trick. Cheers! Jennifer

[endorka]

I finally got the plaster good enough and painted it to match the rest of the room. It'll be a wee shame having to cover most of this with fabric, but there it is!

[garethmetcalf]

That looks really good! Very impressed
Gareth

[Starlight]

Source of the post That looks really good! Very impressed
Gareth

I agree with that. It looks remarkably neat.

[endorka]

Source of the post

The other test was a reference track, Peter Frampton's "Show Me The Way".

Studio version or the now-classic version from "Frampton Comes Alive"????

Studio version. I love the sound on that recording.

[endorka]

Thank you chaps, it's nice to see it coming together at last.

I mentioned earlier doing an ear test of sound transmission to one of the rooms below, the transmitted sound having reduced bass and now being predominantly midrange. I thought it might be interesting to check the transmission loss graph done when the previous simple wall of 12.5mm plasterboard was there - see graph below.

And indeed, after the bass, midrange transmission was the next worse poorest performer. If my ear is to be trusted the bass has improved with the new assembly. I suspect the midrange has too, but perhaps less than the bass. It will be interesting to see if stuffing these traps with insulation cuts down their resonance & reduces the midrange.

[garethmetcalf]

Can you do a measurement now to overlay on the one previously taken? Would be interesting
Gareth

[endorka]

Source of the post Can you do a measurement now to overlay on the one previously taken? Would be interesting
Gareth

Good idea. Once the dust has settled on this project I will definitely do this.

Cheers!
Jennifer

[endorka]

On Friday a friend of a neighbour installed the soffit vents. He did a grand job. These are for 150mm diameter ducts and have flyscreens. There is one on either side of the balcony, they are very white so blend in well. Presumably they will yellow over time like the smaller bathroom one further to the right.

My part in this was to crawl about in the eaves and pass the inner hose to him through the holes drilled in the soffits. Fortunately he was able to attach the hose to the vent with tape and jubilee clip it from outside. Much easier than doing the same in the eaves. For one of them I had to squeeze through the right hand side of this hatch then crawl along toward the end of the bay. It's not too bad once you figure out the sequence of contortions necessary, but I popped a rib by unknowingly placing most of my weight on it along one of those plasterboard edges. It's not the end of the world but it is making further work in that area uncomfortable.

Speaking of further work, I installed the fan in there today. I have two schemes in mind, the first uses a couple of ninety degree elbow joins to turn the corners. I was concerned they would make too much noise, but wanted to try it anyway.

The flex hose coming from the bay to the right is from the silencer. The long hose is from the soffit vent.

The cradle for the fan gets attached first. The joist it is attached to runs along the centre of the stairwell and does not directly touch any of the rooms. Therefore I hoped it would avoid structure based fan noise transmission to them.

Fan now in the cradle;

The good news: there seems to be little or no noise from the fan itself in either studio room.
The bad news: low frequency duct turbulence based noise emerging from the silencer in room 1 is definitely louder than my previous trial using only flex duct. I am 99% confident the 90 degree elbow is the culprit. Therefore I have dismantled this setup, and will try again tomorrow with the fan on the other side of that joist, using no elbow joins, only longer runs of flex duct with much larger radii for the turns. The fan has more than enough power to deal with the extra length of duct this will require.

Cheers!
Jennifer

[endorka]

I redid the ducts from exhaust silencer -> fan -> soffit vent today using only flex hose with larger radii turns than the elbow joins used yesterday. It meant moving the fan to the next along eaves bay. Fan cradle in place and silencer to fan hose attached. The fan is screwed to a small OSB board which is then attached to the top rafter;

Fan in place and fan to soffit vent hose attached. I secured this with two jubilee clips after the photo was taken.

The hose goes round the corner from the fan to the soffit vent 6 feet or so away. Since exiting the silencer, the flex hose circuit has completed a full circle of turns. There was no way to avoid this no matter how things were arranged.

I tidied up a bit in those eaves and put as much insulation as possible in there, tested the fan, then closed the hatch.

Here's the current status of room 1. The eaves bay on the right has a small length of hose attached to the roof soffit. This is for the air supply, and when finished will go through a filter, then the silencer, then another four metres or so of flex hose to the back of the room. You can see my pencil marks for cutting a hatch for access to change the filter from the ceiling of the room below.

I tested the ventilation with the room like this, with the window trickle vents closed.

Good news;
- The ventilation is quieter than the elbow join version
- You can't hear the fan in any rooms of the house except the bathroom directly below the fan. And it's not loud there.
- The fan is surprisingly quiet on the landing despite being only behind one layer of 12.5mm plasterboard. Much, much quieter than the studio computer that is situated there.
- It does actually cool the room! There was plenty direct sun today that would normally make the room uncomfortably hot. With the fan on, it did not

Bad news - the duct noise in room 1 is still a little louder than I hoped for. With a cheap dB meter set to C-weighted slow, it reads 4dB above ambient noise level. It's a low frequency rumble.

But nil desperandum, this is to be expected for two reasons. There is far more airflow at the moment than there will be in the finished system. I suspect more than 6 changes per hour is happening at the moment. This is because the static pressure of the entire system is lower than it will be when complete with several metres more flex duct, a filter and another silencer. Air can also be drawn in through the standard soffit vents on the right eaves bay as well as the ventilation soffit vent, further reducing static pressure. Once everything is finished the static pressure will increase, and the airflow through the vents decrease. Decreased airflow means less turbulence around the vents therefore they will be quieter.

Second is; the minimum cross sectional area of HVAC register to maintain a velocity of less than the "minimum quiet standard" of 300 ft/m must be no less than 339 cm2. The inlets are 20x20cm so 400 cm2, but the intumescent grille reduces this to 224 cm2, too small to meet the minimum standard. This is ok though as I will build in larger registers in the speaker soffits at the front of the room. Probably with a silencing aspect before them too.

Onwards!