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Triple leaf query - sorry - however I live in Australia, differing construction....
Old 3 weeks ago
  #1
Here for the gear
Triple leaf query - sorry - however I live in Australia, differing construction....

G'day guys.

My apologies in advance as a few of the guys that I have read fairly knowledgeable responses from in previous threads are likely *eyerolling* and heading to the next thread. I have done a lot of research on my intended installation (everybody says that!) and I have the benefit of a B Eng (Civil) to help with the technical side of things.

The one snag I have found from other threads and my research is that double brick cavity walls are barely ever encountered...in Western Australia it is very much the standard construction method for EXTERIOR walls.

Anyway in hope of getting some input I will try to get to the point quickly. I hope I can attach .pdf's of my CAD drawings...

Main objective: I am retired at a young age due to being a hard worker in my field and having rich and now dead relatives. I have bought a nice house in an upper class neighbourhood that WILL NOT LIKE THE SOUND OF MY DRUM KIT. As such I am soundproofing a bedroom to decrease the sound transmission. THIS IS the main aim. Yes I am concerned with the interior acoustics but that is a distant second to minimising sound transmission.

Where the triple leaf issue comes in is that the typical 'Gervais et al' direction is to head towards a RWAR. No problem. I will state up the front (without intent to be arrogant!) that flanking paths, the weak point being the ceiling and roof space, construction methods etc I am confident enough with. The reason I want to bluntly put this forward is that too many posts I have read start one place and end up somewhere else...I am sure that I would benefit from the input of others here regarding those other items; I just don't want to confuse the actual question.

So the problem is shown in my attached pdf. It is a brand new house however I did not build it so I am stuck with a retrofit. My apologies for the surrounding garden design etc. It is obvious enough that I have two walls to the exterior of the bedroom that is shown that are double brick construction. Initially I considered knocking down a wall to Bed 5 or Bed 3 and creating a much larger and more dimensionally comfortable area; however i am not 'building a pro studio' and I have plenty of other things to drop that $20k on...so I ruled that out. Hopefully that hints at my budget being OK but any particular solution would need to justify it's cost *cough GG*

When I say 'double brick' I mean that they are 90mm wide brick walls (rendered/plastered on the inside and outside leaf) with a 90mm cavity between the two. The two leaf's ARE JOINED BY brick ties and there is no insulation in them; both standard practice. I am fairly certain that insertion of insulation in the cavity breaches Australian Standards; could be wrong.

So after some research I set off to build a RWAR. I have detailed plans of the intended stud construction and materials take off sheets and the like. Now I am looking at the business end of the job (buying stuff!) and I simply cannot proceed without ruling out the potential triple leaf issue OR allowing for it.

So my query is: if I decide to construct a stud wall type room within a room; will I have issues with the triple leaf effect on the two sides that are double brick construction?

Notes:
The proposed construction is (from outside in on the double brick walls):
90mm rendered brick wall exterior
90mm cavity (with brick ties between leafs)
90mm rendered brick wall interior
Approx 70mm gap/cavity
90x45 (4"x2") studs with insulation
Two layers of gyprock ('dry wall' in American )
They will be joined with a glue of course...

1. The sound transmission through the house DOES NOT MATTER. A benefit of being single...and if she existed she could love it or leave...
2. The 'boundary wall' to my neighbours houses on either side are around 8-10m (haha...try 25 - 30 feet!) away. Both boundary walls are solid (single brick construction) and both neighbours have living areas that are around another 10m/30feet from the boundary wall.
3. I have not used isolation clips due to their prohibitive cost in Australia. The cheapest isolation clip (resilient mount?) is around $6 Australian. Add the channel and it faces a simple cost/benefit ration. I DO NOT debate that resilient mounts are effective...I debate their efficacy based on the cost. If they are the 'gold standard or you're screwed bud' then that is fine...I have the money and will reticently drop for them.
4. The dimensions of the room will have stuck out already. Yes i unfortunately have the dreaded square room. My intent was to heavily diffuse one wall. No other option...dimensions of the room are 3270mm x 3100mm exactly.
5. Again reiterating that the room will squish in my Mesa Stack and Drum Kit so the main focus is increasing the sound transmission loss. It seems that an STC rating is still used in America? In Australia there is a combined Rw +Ctr value that also includes an allowance for impact transmitted noise. In realtion to the Rw + Ctr number I would be stoked with around 50. I am not 100% how that correlates to an Stc number...say Stc 50?

I have noticed that a number of posts give limited details of what their intent is and have seen the same question asked a number of times by subsequent guys that were decent enough to reply. Correspondingly I have done the opposite and included every detail I thought may be relevant and this is a goddam essay...sorry! Any who make it through this...thanks for bothering to read it all! If you can offer any assistance (with the main query or other topics...actually I am obviously new here so links to other threads would also be appreciated).

Any advice would be appreciated guys.

Cheers
Peace
Attached Files
File Type: pdf Drum Room.pdf (977.1 KB, 22 views)
Old 3 weeks ago
  #2
Gear Addict
 

STC = Rw, plus or minus 1.

Ctr is about -3 for single leaf construction, -8 for double leaf and maybe up to -12 for triple leaf.

STC only looks at sound transmission from frequency bands 125Hz and up.

Rw only looks at sound transmission from frequency bands 100Hz and up.

There is an additional Ctr parameter, Ctr50-5k, which is more relevant to a drum room but very little data is published for that frequency range.

The answer to your question has been provided before in this forum...

The answer starts with: How much sound insulation do you need...

There is a sound source - drum kit.
There are sound transmission paths, via walls and roof-ceiling and window, yet to be determined.
There is distance, which will provide sound sound reduction.
There is a noise receiver at the neighbour's. How quiet is it?

The math is something like:

Receiver Level = Source Level - Sound Transmission Loss (STL) - distance loss

To know what STL is required, requires knowledge of how quiet the end result is required to be.

If you are going to play drums during daytime then the STL required is probably different than if you want to play at 3am, even occasionally.

What you propose, construction wise, looks ok. However, is it a single storey house? What about the window? Roof-ceiling?

Also, the other two walls of the room, not the external ones, will still leak noise to the outside and may need to be addressed.

You may need the services of a professional acoustic consultant. There are a couple of good ones in Perth.

Regarding the brick cavity, it can be insulated by retrofit using hydrophobic materials such as: https://www.knaufinsulation.com.au/p...fil-carbonplus

I think DIY in this case may be "suck it and see". Otherwise, see a pro. Otherwise, Step 1 would be to measure the background sound level at the neighbour's in octave bands at a few different times of day/night. That requires an octave band sound level meter. Step 2 measure your drum kit in octave bands. Step 3, ... well it requires more knowledge after that.

Not sure how much I helped.
Old 3 weeks ago
  #3
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avare's Avatar
 

+1 to what Sebg wrote.

Resilient clips will make isolation worse. You probably need nothing added. See NRC IR. 586 fig 11 lower right corner. Enjoy the cost savings!
Old 3 weeks ago
  #4
Here for the gear
Firstly: thank you both for your time and replies! I was beginning to think that I had wasted a half hour...but not so in the slightest...

Quote:
Originally Posted by avare View Post
See NRC IR. 586 fig 11 lower right corner.

Resilient clips will make isolation worse. You probably need nothing added. Enjoy the cost savings!
I had no idea such a document existed...I have found it and have some reading ahead of me...my thanks for the reference! That is extremely helpful and greatly appreciated!

Quote:
Originally Posted by Sebg View Post

Ctr is about -3 for single leaf construction, -8 for double leaf and maybe up to -12 for triple leaf.

There is an additional Ctr parameter, Ctr50-5k, which is more relevant to a drum room but very little data is published for that frequency range.

The answer to your question has been provided before in this forum...

You may need the services of a professional acoustic consultant. There are a couple of good ones in Perth.

Not sure how much I helped.
Well...I will start with your response has been very helpful; thank you for your time! I have quoted the parts of your comment that I especially appreciate; of note you mention professional acoustic consultants in Perth? As it so happens I live in Perth (though about as far North as you can go!) and would appreciate some contacts if you are able. I am a B Eng (Civil)...I think I mentioned that before? Anyway any acoustic professional's input is welcome as I should hopefully be able to get what they are talking about. Whilst I intend to DIY I am certainly happy to pay for professional advice.

I believe that mostly your questions were intended for my own personal checklist so I won't answer them all and expect a response...though I appreciate the note on a number of them...I had not thought the single walls would present an issue as they led into other bedrooms (one as a study and the other as storage) so I will have a good look at that!

It also seems that whilst I have spent a lot of time looking on this site (and others) for a similar approach and similar issues; I obviously have not looked hard enough...so I will get back to looking!

I appreciate both of your replies gents...perhaps if it is useful to any I will post my eventual process...regardless thanks for your time

Cheers
Old 3 weeks ago
  #5
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avare's Avatar
 

Quote:
Originally Posted by CaptainBuff View Post
Firstly: thank you both for your time and replies! I was beginning to think that I had wasted a half hour...but not so in the slightest...



I had no idea such a document existed...I have found it and have some reading ahead of me...my thanks for the reference! That is extremely helpful and greatly appreciated!



Well...I will start with your response has been very helpful; thank you for your time! I have quoted the parts of your comment that I especially appreciate; of note you mention professional acoustic consultants in Perth? As it so happens I live in Perth (though about as far North as you can go!) and would appreciate some contacts if you are able. I am a B Eng (Civil)...I think I mentioned that before? Anyway any acoustic professional's input is welcome as I should hopefully be able to get what they are talking about. Whilst I intend to DIY I am certainly happy to pay for professional advice.

I believe that mostly your questions were intended for my own personal checklist so I won't answer them all and expect a response...
So you do not want our help? We can not with out more information.
Old 3 weeks ago
  #6
Here for the gear
Quote:
Originally Posted by avare View Post
So you do not want our help? We can not with out more information.
Well...hell yes if it is offered in such a manner! Possibly some crossed wires on my part...

I guess I am somewhat cautious in new forums or just forums in general. It seems that it is easy to step on toes. I don't want to look like a leech wanting someone else to spoon feed them the answers; but at the same time I have never done this sort of thing before and despite having spent many long nights researching and on CAD I am no professional and don't want to come across as an arrogant ass. Which is probably kinda like what I am sounding like now.

An example of what I am talking about is going to any forum and mentioning the word 'audiophile'. It seems a good word choice to elicit instantaneous arguments.

With honesty and no offence intended; the mention of 'The answer to your question has been provided before in this forum...' coupled with the lack of an actual answer to my question in Sebg's reply led me to think that I should be doing some research and moving along...

My apologies as I seem to have taken that the wrong way - I didn't see it as 'we need more information to help you out' but more the aforementioned 'we aren't spoon feeding you mate; look at all these things you have to consider'. My apologies to Sebg for any offence; I am simply stating the truth as I saw it.

Having established that there are some decent folk about on GearSlutz I will provide all the details I can...I have many standard details and specifications, notes, books and numerous CAD drawings that I am happy to put down. Any (constructive) points that anyone wants to make are welcome. Criticism is normally best done constructively IMHO. It probably sounds like I am a soft little petal right about now! Unfortunately the username is a nickname and is for a reason...

Having talked enough BS I will list at least something useful:

I am 38, retired (Oz was a good place to get a lot of money when I came out of university/college...oh; and money in my now mostly passed on family), B Eng Civil, mortgage free 5 bedroom and 3 bathroom single storey house next to the beach. Exactly the sort of area that is predominantly retirees. Needless to say they are a bunch of whining little runts. Just starting my MY17 WRX and exiting my property via my driveway has annoyed the 'walking dead' on my left.

I bought in this area due to the walking distance to the beach (and more importantly the beach pub...I am an Engineer after all ) and the lack of crime. The retiree phenomenon is a small price to pay for those things IMHO.

Related to my house; I will get back to you with some .pdf CAD drawings and a summarised as much as I can list of specifications, standards, fascist local council rules and other details. However off the top of my head I have a metal roof (awesome ), brick or double brick construction. There will be a double door arrangement, stud wall room within the existing bedroom, I have structurally designed the stud walls/ceiling and hence the ceiling of the interior stud room does not touch the exterior bedroom ceiling (this bit needs to be treated carefully and include a disclaimer...and it is open to 'you screwed up mate'; though I see no reason how that could be), the window will be sealed in, I have a simple air con system (unsure exactly where best to vent the thing though...)...I will include a list of products that are easily/financially viable to source as well.

I stumbled upon a grandiose fuster cluck as I was looking in the roof today as well...so I will have to self deprecatingly include a photo or two of the issue.

I appreciate the offer of assistance and apologise for misreading it initially!
Cheers guys
Old 3 weeks ago
  #7
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If you must triple leaf use as small a gap as possible. See IR-586 fig 5 and note the trend between depth and reduction TL.
Old 3 weeks ago
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Quote:
Originally Posted by avare View Post
If you must triple leaf use as small a gap as possible. See IR-586 fig 5 and note the trend between depth and reduction TL.
To my knowledge no such research has been done in Australia to any degree like this. There is the 'Gyprock Red Book' but it is ONLY theoretical and bigoted to it's own products anyway (CSR). Canadians rock...and I have a lot of reading to do...

Many thanks avare...incredibly helpful!

Cheers
Old 2 weeks ago
  #9
Gear Addict
 

Quote:
Originally Posted by CaptainBuff View Post
To my knowledge no such research has been done in Australia to any degree like this. There is the 'Gyprock Red Book' but it is ONLY theoretical and bigoted to it's own products anyway (CSR). Canadians rock...and I have a lot of reading to do...

Many thanks avare...incredibly helpful!

Cheers
Sorry, I had to laugh at "bigoted to it's own products". It IS published by a manufacturer after all. Boral's "System+ Plasterboard Selector" (now USG Boral after a deal with US Gypsum) also only includes its own products.

What is the existing ceiling height? Also, is the floor slab on ground?
Old 2 weeks ago
  #10
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Quote:
Originally Posted by Sebg View Post
Sorry, I had to laugh at "bigoted to it's own products". It IS published by a manufacturer after all. Boral's "System+ Plasterboard Selector" (now USG Boral after a deal with US Gypsum) also only includes its own products.

What is the existing ceiling height? Also, is the floor slab on ground?
Haha No need to apologise! I had a good laugh at:

Quote:
Originally Posted by Sebg View Post
Receiver Level = Source Level - Sound Transmission Loss (STL) - distance loss
As with the Boral system though; all information I have come across down under is manufacturer provided. I believe the BCA (or NCC) specifies two methods of 'approval' for acoustic systems:
1. 'Deemed to comply'. Pick a system from any such manufacturer provided information, build that, and you have met the requirements.
2. Actually do some insitu testing to prove your system meets requirements.

No surprises as to which system builders go with...and hence the lack of documented testing on much.

As to requirements: 1 of the 3 volumes of the BCA/NCC deals with Class 1 buildings (a house that someone would live in) and eventually gets to the requirement of 'Rw + Ctr = 50'.

As an Engineer I consider such useless taxpayer funded frivolity quite humourous as well! It seems that Canada (and perhaps others) are actually progressing in the direction of testing based requirements...sort of like what Engineers use when they are doing the drawings for the builders.

However I digress. To answer some of your questions:
Room is 2600 mm or 8' 6.3" high. That is from top of carpet to bottom of gyprock ceiling.

Floor slab is on the ground...as in it is a single storey house and the floor is a 100mm (4") thick concrete slab with edge thickenings directly laid on compacted natural ground. On top of the slab is either tiling or carpet. In this room it is carpet; which consists of a ~5mm underlay and some carpet on top of that.

Briefly related to STL requirements; I believe in my meanderings I stumbled on someones 'tag line' stating 'there is no such thing as too much sound isolation'. In simple terms that is my intention. I say that as establishing the variables to the above quoted equation is not possible. Factors such as perception of sound and existing construction limit the ability to quantify these variables...I suspect that is a common issue.

I would love to be playing at the moment (3:17am local) however that is not feasible! So yes...playing would be kept to the mid morning to mid afternoon period. The local council actually has a law in place stating that any musical instrument that is audible can only be played for one hour per day. Sieg Heil. Enforcement of said law I am unaware of...it would certainly be interesting!

Installation of loose fill cellulose or similar is a great idea...I initially thought that was rubbish but after reading further it should likely be step 1. Efficacy will be decreased by the brick ties between leaf's. There is access to the cavity from within the roof space so it could possibly be done DIY...operating on the assumption it can be bought in DIY manageable form...unsure; need to research more.

STL requirement...I believe 'suck it and see'...? Any acoustic professionals in Perth that can be recommended would be welcome...bearing in mind there is no national accreditation of this field so I will only be guided by suggestions.

Thank you both for the help!
Cheers
Old 2 weeks ago
  #11
Gear Addict
 

There is no accreditation body but the largest and most well known professional body is the AAAC (Association of Australian Acoustical Consultants).

https://aaac.org.au/member-firms

There is also the Australian Acoustical Society but that is not specifically for professionals in the field - anyone with an interest in acoustics.

https://www.acoustics.asn.au/joomla/
Old 2 weeks ago
  #12
Here for the gear
Thanks for that SebG

I found links to those sites from - I think it was a research paper or something similar? - anyway I had a look at both of the sites and had the feeling that it was designed at commercial interest rather than residential. I had a brief read of the Acoustics Australia Journal (the backdated versions anyway!) and they were mostly a wee bit over my head in terms of acoustics! Good to see that there was a group providing acoustic information to the public though. Although I was unimpressed to see that one could pay for membership to the AAS - and if they demonstrated exceptional contribution to the acoustic industry (unknown criteria) they could be elected as a 'Fellow' of the Australian Acoustic Society - I guess at least it is a start.

I remember that I had to be a Member of the Institute of Engineers Australia as a part of my engineering degree. Having provided me nothing of use (other than some extra letters after my name; which I have never claimed anyway) when they sent a 'renewal notice' that had membership fees without student discounts...well yeah.

Cool story. Anyway thank you both for your help! I suspect that you may be Australian SebG but in the Eastern States? If you work in the industry and are domestic then I would appreciate being able to talk to you or engage your services to some extent. If not then I appreciate the assistance all the same

Cheers
Josh
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