Attic Shaped Studio

#31

Addressing the crack along the rear wall / floor corner more or less as per Stuart's instructions.

The cut down top board sections used to reach the wall were happily not glued to the sub floor and so easily removed. The rest of the top boards were glued. They are decent tongue and groove system, so with that and the glue should be fairly well sealed.

Revealed, the dark side is! :shock:

Remember this chasm is nearly 3.5m long, and is above one of the rooms I specifically want to reduce sound to! The amount of sound leaking through this must have been staggering.

On the upside, it allowed me to determine the exact thickness of the sub floor (22mm) and top floor (18mm). 40mm total, not too shabby, and useful to know for structural load calculations if I want to add mass below. And it's also good to establish there is decent insulation in there.

This goes on for nearly the entire width of the room, 3.5m.

Saw the drywall to an even height a few mm above the planned repair;

No room for the circular saw, and no possibility of replacing cut top boards, so I extended the sub floor to its proper dimensions (or greater) with these 20x20mm sub spacers cut to fit snugly around the joists. A pretty quick job.

Tons of caulk to seal to the existing sub floor;

The top spacer (20x15mm) has been added onto the sub spacer. It stops a few mm short of the cut drywall. The top floor edge bit have also been reinstated.

The backing rod is amazing stuff, thanks for the tip Stuart. 6mm diameter here. I used a marker pen to mark the correct depth on the scraper used to push it in the the gap.

Sorted!

I'll let the caulk settle then add a bit more just to make sure.

My "Caulk Fu" must have gone up a level or two since doing this particular exercise

#32

Wow! Excellent work Jennifer. That hole looks like you had a pretty major leak, as you mentioned. Once you finish that up, it will be good to do some more testing, to see how much of a difference it makes. My guess would be: "Very noticeable".

The backing rod is amazing stuff, thanks for the tip Stuart. 6mm diameter here.

: thu: There's lots of techniques like this that can help make a difference, but that most people don't know about...

I used a marker pen to mark the correct depth on the scraper used to push it in the the gap.

... and there's a new technique! I love it! I normally do it with a screwdriver or sliver of wood, but no depth marking, except a rough estimate with my fingers: putting that depth marker on the tool is a smart move: ensures you get the rod in the right place for the best seal, while minimizing air gaps. We'll have to baptize this one: "The Jennifer Backer-rod Technique"!

- Stuart -

#33

Nice one!

I can already hear the difference with that and all the other improvements with just my ears. In terms of the absence of sound, I thought the room was pretty quiet before, but now it is very quiet. Almost as if a bunch of sound you wouldn't be consciously aware of unless it stops is no longer there. The effect is strong enough to give the room a different (better) ambience. This has actually taken me by surprise, and I like it a lot. The loudest thing in the room now is unquestionably the noise coming through the windows, even with the vents shut. And only because everything else is so quiet. It's actually quite reassuring to know we've reached the limits of the room in that respect.

Transmission of sound to other rooms and the landing has audibly improved as well. I recorded a sax player in here today and had a wander about the house listening while he warmed up. Sax was one of the more pervasive instruments for sound transmission, and it definitely has been reduced. I've noticed loads of similar things like this, and the difference between sound transmission from this room compared to sound transmission from "untreated" ones is striking.

I'll do some more proper testing, but there's more improvements to be made yet, off the top of my head;

- LED downlighters to replace 11 halogen ones that illuminate the bathrooms below that section of eaves I've been dealing with. The insulation was skimpy because you can't put insulation over halogen downlighters. It's also 11 acoustic holes into the floor below. That eaves section is nearly 6 metres long and runs alongside both room 1 and room 2. I've bought acoustic and fire rated ones you can place insulation over, they can be properly sealed and are much beefier than the standard issue types. Once the electrician has installed them I'll put a decent amount of insulation in there and dampen down that resonant cavity!

- put gaskets on the two hatches in room 2 leading to the eaves.

- Putty pads on the considerable amount of sockets in room 2 and the 2 rooms below room 1. Caulk or putty gaps around pipe runs in the walls and wall / floor corners where possible too.

The plan is to get as much out of the current setup as I can, then proceed from there.

Cheers!
Jennifer

#34

Here's a small but perhaps worthwhile isolation improvement that only took a couple of minutes. It's only necessary to lock the studio door from the outside, so why not fill the inside keyhole with putty from an offcut of the socket putty pads?

A bit of a layer in the door itself;

A black plastic square so it still looks a bit like a keyhole rather than red putty;

Fill the circle with putty. It was fascinating how heavy this became compared with the "empty" circle; felt almost like something made from solid metal. Just demonstrates how dense that putty really is;

Done!

Cheers,
Jennifer

#35

Nice work! Just stumbled on this thread!

#36

Thank you! I've done quite a lot since the last update, time for another update soon I think.

Cheers,
Jennifer

#37

As per my riser post, I've finished the 8x6 foot modular riser and initial sound isolation improvements. I did before and after measurements and am preparing a post about these.

I also installed a proper 16 + 4 stage box with 15m cable routed from the preamps in the front left corner to the centre of the other side of the room. To get there in a concealed manner it has to go up a wall diagonal, across the ceiling and back down the opposite wall. Fortunately there was a neat route for this that allowed the cable to go behind acoustic panels for most of the route whilst avoiding mains or lighting cables.

Previously there were a couple of multicores going round the floor / wall edges, mostly concealed behind floor / wall bass traps. It worked but was untidy and did my head in at times. The stage box is better in every way, and means I can take out many of the wall / floor bass traps to give more room when recording without exposing tons of ugly cabling. The room looks far more inviting this way I think.

(The nasty looking screws sticking out the wall are to hold the angled floor / wall bass traps when in place. I've since removed them and will replace with a white rubber door stop instead)

Cheers,
Jennifer

#38

Here are some pictures showing the difference in sound transmission loss to various rooms after the many improvements discussed previously in the thread. These improvements are listed after the pictures along with test details.

The sound source is a bass amp in Studio room 1 emitting unfiltered pink noise. This was measured at 105dB, C weighted slow, at a distance of 1m from the speaker front.

The annotations denote;

The sound isolation improvements were done between sessions when time permitted;

Studio Room 1
All holes in walls repaired, patched or filled to at least plasterboard surface density. Some of these were very large.
Putty pads applied to all sockets and light switches. There were about 20 sockets in total, half of them double gang.
Holes in ceiling for lighting wires puttied or sealed.
Holes for radiator pipes sealed.
There perimeter of the room where the wall meets the floor was thoroughly caulked.

Landing
Hatch to eaves fitted with weather stripping along perimeter to ensure seal.
Back side of hatch to eaves covered with insulation
Putty pads applied to all sockets and light switches.
Holes in ceiling for lighting wires puttied.
Floor / wall edges caulked.

Eaves
11 halogen downlights to two bathrooms below replaced with acoustic, fire and insulation rated LED equivalents.
Almost an additional 5 square metres of 170mm thick loft insulation added to existing (sparse) insulation.

Studio Room 2
Floor / wall edges to landing caulked.
Perimeter and drop down seal added to door to landing.
2 hatches to eaves fitted with weather stripping along perimeter to ensure seal.
Back side of hatches to eaves covered with insulation
Putty pads applied to all sockets and light switches.
Holes in ceiling for lighting wires puttied.
Holes for radiator pipes sealed.

House Room 3
Putty pads added to vast majority of sockets and light switches.
Holes for radiator pipes and hot water tank pipes sealed.
Holes in ceiling for lighting wires puttied.
Perimeter seal fitted to door.

House Room 4
Putty pads applied to all sockets and light switches.
Holes for radiator pipe runs sealed.
Hole in ceiling for lighting wires puttied.
Perimeter seal on window repaired.

Notes
I estimate a total of around 60 wall sockets were treated with putty pads.
I fitted a perimeter and drop down seal to Studio room 1 door prior to the "before" measurements.
Studio room 1 and 2 and landing floors are 40mm thick; 18mm tongue and groove real wood on a 22mm subfloor.
Walls are 12.5mm plasterboard on both sides of 4x2 studs. The cavity is stuffed with fluffy insulation.
Joists between floors are 220mm, the cavities have fluffy insulation in them.
Doors to landings or hall from room 1, 2, 3 and 4 are FD30 solid core fire doors about 45kg giving 27kg/m2 surface density.
Doors to wardrobes, bathrooms etc. are lighter, presumably hollow core.
Doors to hall from room 5 are single glazed glass doors with an audibly poor STC.

Test Notes

I performed sound transmission level tests before and after the improvements. The signal was sent through a bass amp in studio room 1 and measured in each room with a UMIK-1 calibrated measurement mic and REW. For rooms adjacent to studio room 1 (rooms 3, 4 and the landing) precise positions of amp and mic were noted and recreated for before and after tests. Mic positions in other rooms were recreated from photos.

The sound source was unfiltered pink noise through the bass amp at 105dB. The bass amp was on the 6x6' version of my modular riser. Unfortunately I did the "before" test with the pink noise high pass filtered :oops:

The improvements had already been made when I realised this, so there was no opportunity to re-measure properly.

But fortunately I used the same bass amp on a prototype riser with unfiltered pink noise at 105dB to perform the tests near the start of this thread. The mic was also the same distance from the speaker. One difference was the position of the bass amp, which was closer to the centre of room 1. For most rooms the difference in distance between source and measurement mic is not significant, except, perhaps, the landing...

Another difference was the measuring device. The early tests were done with a fairly cheap dB meter. I checked the readings alongside the calibrated UMIK-1 mic and noticed the dB meter read 3dB too quiet below 80dB, but true at 105 dB. So the initial sound transmission reduction measurements at the start of the thread were incorrect. The reduction of sound between rooms was actually 3dB lower than posted, i.e. worse. The other more detailed test I performed correctly confirms this. I'll describe this test in a later post.

In the meantime I adjusted the figures in this post to the true properly calibrated levels.

#39

Some quick thoughts before I post the more detailed test. It's worth mentioning that none of these were "improvements" as such, more like making good aspects of the house where sound isolation had been weakened due to installation of sockets, pipes, light fittings and so on. There were also repairs to some large holes in walls and of course the obligatory caulking along floor/wall edges.

The materials didn't cost much but I spent a lot of time doing them, but the effort was totally justified. Having crazy loud unfiltered pink noise to adjacent rooms reduced by between 4 and 5 dB is a big difference. And in "real world experience" terms the difference is even greater. For example, I have the studio computer sitting on the floor of the landing. You could hear its fan loudly in the bathroom below. Since the installation of the putty pads in the landing and the acoustically rated downlighters in the bathroom, you can't hear it at all. I've made similar observations throughout all the improved areas. I used to be able to hear music at 80dB on the Studio room 1 monitors in Studio room 2. Now it is barely audible at all.

The relatively poor performance of House room 5 is almost certainly due to sound from the landing going down the stair well, through the poor STC glass doors and into the room.

It would seem that sound transmission to the landing from Studio room 1 is now actually half a dB worse than before! Fortunately it's just a glitch due to the amp being closer to the centre of the room 1 for the "before" test. For this measurement the added metre or so difference was significant enough to cause this. For rooms below and further away the difference in distance was not significant. The more detailed and correctly done before and after tests confirm this.

Cheers!
Jennifer

#40

Here's the more detailed test for Room 3 using sweeps from REW. The methodology seemed like common sense, but if it is flawed please let me know and I'll do the calculations some other way. In retrospect it would have been better to do several sweeps in different positions in each room, but there are only so many hours in the day, alas!

First task was to get the "after" amp and signal generator setup in Room 1 as close as possible to "before". The same gain and position setup as the (correct) pink noise one! A perfect match wasn't possible, perhaps due to the presence of the 6x6' riser in the "after" room, but it seems pretty close. In particular I tried to match the level of low frequency sound energy in the room as closely as possible;

Next take the measurement mic to room 3 and repeat the sweep with the amp directly on the floor. The amp was directly on the floor for the "before" tests too. Here are the before and after sound isolation improvement measurements;

Another sweep with the amp on the riser. The amp was in the same place (albeit ~100mm higher), it was the riser I moved. The graph shows the "after on floor" and "after on riser" measures;

For interest, a comparison between the before and "after on riser";

Next, use REW trace arithmetic to generate the transmission loss curve by subtracting room 3 from room 1 for the before and after sweeps. I used divide for this because the dB scale is logarithmic - is this correct?

And finally, a comparison of the transmission loss of "after" and "after on riser";

Please let me know if the method was valid, and I'll post the equivalent results for the other rooms.

Cheers!
Jennifer

#41

Great read Jennifer!
It must be gratifying to know that all that time and effort has paid off! It's also interesting to know that significant gains in T/L can be made without spending a lot of cash. Your attention to detail is an example for us all (certainly me)!

#42

Thank you John.

Yes, the biggest factor in these efforts was time. And they would take far, far less time if done properly in the first place. One case in point being the 3m long hole between floor / wall edge at the back of the room described earlier in the thread. It was completely hidden behind the skirting board so visibly ok but terrible for sound transmission. It took several hours to fix, but would have been easy to fix properly in the first place before the plasterboard went on. But as mentioned in Rod Gervais' book, for some workmen, if the flaw can't be seen then it's good enough.

The acoustic and fire rated downlighters were similar in a way. They only cost a couple of pounds more than the all too common cheaper tin circles, but make a massive difference.

The putty pads alone made a huge difference. There are a lot of sockets in our house though, so plenty of gains to be had there. Applying them to the back of a socket is easy, applying them to the inside is a bit trickier at first, but by the time I had done 50 or so it was only taking a few minutes.

I could go on and on LOL! :-)

Cheers,
Jennifer

#43

Wow! What an incredibly detailed, careful, and meticulous evaluation, Jennifer! Awesome!
The results speak for themselves. Impressive.

endorka wrote:Source of the post Next, use REW trace arithmetic to generate the transmission loss curve by subtracting room 3 from room 1 for the before and after sweeps. I used divide for this because the dB scale is logarithmic - is this correct?

Dividing gives you the difference between the two. So for example if you divide the left speaker by the right speaker, that shows how well matched the are: the difference between them, which ideally should be a flat line along the 0 dB mark, but in reality will vary a little up and down. So if you divide the "before" by the "after", then the resulting curve is the difference: how much EXTRA isolation you are getting.

Thanks for posting those results, by the way: The improvement is very clear, and undoubtedly very audible! A lot of hard work, for sure, but the results speak for themselves. I'll bet your clients are happier too, and your tracking sessions should go more smoothly now: you won't be double-guessing so much now, trying to decide if what are hearing is coming from the speaker alone, or with "help" coming through the walls from the other room.

So what's up next? Are you going to do the HVAC part, or the room optimization and tuning part?

- Stuart -

#44

Cheers Stuart. I recorded a six piece rock band here last week, all playing live at once;

The difference from before was significant. Far better isolation and separation than before which helped get better headphone mixes and so on. Also the option to have better recorded separation too, if desired! Going for a brighter / more ambient sound (as you have mentioned) by temporarily removing some of the floor / wall bass traps helped a lot too. Great for drums! That and the more spacious visual aspect was really enjoyed by the band, who have recorded here before. So many thanks again for your guidance towards this.

Next up is the HVAC, I have a design almost ready.

Alongside that I plan a few improvements to the sound isolation that won't take long but I think make a big difference. Justification by tests and graphs to follow :-)

Cheers,
Jennifer

#45

endorka wrote:Source of the post The difference from before was significant. Far better isolation and separation than before

I'd call that "success" then, for sure! That's what its all about: Making better music, and making it more enjoyably.

Looking forward to seeing your HVAC design!

- Stuart -

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