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Sound Proofing...When do you have enough?


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My music room where my measurements were taken is like a storage warehouse for a fibreglass factory.  It is not a "normal" room by any means.  You can hear the difference to other rooms even as you walk in.  That it measures so low is not surprising to me by any means.

 

My meter is a cheapo ($20) A-weighted from Jaycar used primarily to check the loud bits.  It is slow to react and slow to decay so the numbers are very much an average.  I have a DEQX used to make measurements before generating filters, but am scared to use that to measure baseline SPL in case of feedback (yeah I know I could switch the power amps off).  Too lazy ... so unweighted SPL across the freq range remains a mystery.  Whatever, my room is very very quiet pretty much all the time.

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2 hours ago, Al.M said:

Perhaps others who earlier reported 15-25dB noise floors in their houses could list their equipment prices and models.

I would bet nobody has a microphone capable of measuring this level even close to reliably.

 

Just did a quick check on a >$1000 temperature compensated measurement microphone, which lists it's own inherent noise as 20dB(A) .... so anything even remotely close to 20dB is going to be pretty inaccurate.

 

The reality is that people who create microphones which can take 80, 100, 120+dB

, aren't optimising these same microphones at <40dB

 

22 minutes ago, almikel said:

...of course my wife can't put up with wearing ear plugs :(

:D 

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On 17/01/2019 at 12:28 AM, Silent Screamer said:

Are you southside or northside? Guessing southside if you can hear the freeway.

Coorparoo

 

On 16/01/2019 at 7:59 AM, davewantsmoore said:

... but this is plenty low for a playback system, yeah?!?  :) 

From recollection, 30dB SPL C weighted is the quietest I've ever seen the SLM measure...I've typically used "C" weighting, although based on the new measurements below maybe it was on "A" weighting to get the 30dB reading???  The SLM always turns on in "A" weighting, so quite possibly my recollection is inaccurate and it was 30dB "A" weighted.

 

...just went and measured the room...in between plane flyovers and trying to avoid footfalls in the lounge above...

...cheap Digitech Sound Level Meter QM-1589 (they sell them at Jaycar).

The Digitech has a "Fast/Slow" button, an "A/C" button and a "Lo/High" button.

 

At 7pm at night just on dusk with birds still chirping, neighbour's pool pump running, TV on upstairs, avoiding plane flyovers

On "Slow", "Lo", "dBA" it reads around 34

On "Fast", "Lo", "dBA" it reads around 35

On "Fast", "Lo", "dBC" it reads around 47...poor process...I didn't get a "slow" reading...

 

New measurements at 7.30pm, no birds chirping, but neighbour's pool pump running, TV on upstairs, avoiding plane flyovers

Fast/Lo/dBA 34.8

Slow/Lo/dBA 35.1

Fast/Lo/dBC 45.0

Slow/Lo/dBC 45.4

 

On 16/01/2019 at 7:59 AM, davewantsmoore said:

... but this is plenty low for a playback system, yeah?!?  :) 

Mostly - it would be great to have better room isolation for plane flyovers (we're on a flight path for landing planes).

With the stereo at lower volumes to be able to have a conversation in the room, I never hear external noise sources other than plane flyovers.

When the stereo is cranked, even listening to classical music with quiet passages, I never hear any external noise sources (I've never noticed any plane flyovers).

 

Back on topic, I don't think the OP's room noise floor is in any way an issue in the OP's case - building the room to achieve sufficient isolation to the master bedroom above will meet all other noise goals - including not annoying the neighbours.

 

With a decoupled room, it shouldn't be too hard to get the "in room" bass response managed also.

 

cheers

Mike

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2 hours ago, aechmea said:

My music room where my measurements were taken is like a storage warehouse for a fibreglass factory.  It is not a "normal" room by any means.  You can hear the difference to other rooms even as you walk in.  That it measures so low is not surprising to me by any means.

Hi Aechmea,

that's an interesting observation, as I also have lots of absorption in my room, but don't get much/any noticeable difference in the "quietness" of my room - likely due to having all the windows/doors always open for breeze in the Brisbane climate.

I've never regarded room treatment as being able to change the "isolation" of a room, only the "in room" sound, and leakage (in and out) will remain similar regardless of treatment???

 

cheers

Mike

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4 hours ago, almikel said:

never regarded room treatment as being able to change the "isolation" of a room, only the "in room

Unless the room is purpose built from the beginning or seriously retrofitted then isolation is unlikely, Depends if your treatments have been installed adhoc/guesswork or through expert advice through measurements.

 

It depends on what are the external and internal noises and whether the room treatments are appropriate for them.

 

Opening windows will increase internal sound levels by 10-15dB(A)+ and negate any good isolation and wall/ceiling STC.

Edited by Al.M
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5 hours ago, almikel said:

New measurements at 7.30pm, no birds chirping, but neighbour's pool pump running, TV on upstairs, avoiding plane flyove

Try measuring later after 10pm and 2am as there is dramatically less outside traffic and urban noise. Assuming your meter mic is accurate those figures are not bad.

 

We use $12k Brüel Kjær 2250 meters that have 16dB(A) and 1dB linear noise floor spec and often place them in peoples houses continuously recording overnight to catch noisy infrequent events and notice how quiet it gets from 2-4am.

 

6BEE6AAF-312A-4685-8C0D-021F870F85F3.jpeg

Edited by Al.M
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This quiet house design link listing house design measures may be useful, scroll down after maps, https://satterley.com.au/documents-and-media/documents/wa/allara/builder-resources/allara-stage-3-annexure-9-copy-of-relevant-documents-quiet-house-design-packages.pdf

 

A lot of modern housing near noisy transport corridors like highways, rail and plane flight paths are required to have quiet house design measures specifying thicker glass (6.38 to 10mm laminated) and less window wall ratios, air conditioning systems that allow windows to be closed to keep noise out, bedroom windows facing away, closed eaves and roofing systems decoupled from Soundcheck ceilings and R4 insulation etc. 

 

The noise floor in such houses would be lower than average houses although the traffic would keep it up. 

 

Edit: Also, many houses built in the last 10 years with have the highest energy efficiency ratings, which in some material situations will even exceed what is needed for good STC. For example, ceiling insulation of R4 is about 200mm thick whereas  good ceiling sound insulation is around R2.5 and entire new house builds are not meant to have air leaks so helps with acoustic sealing as well. The only thing that is not addressed with energy efficiency design that helps acoustics is the thickness of windows.

Edited by Al.M
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9 hours ago, almikel said:

Hi Aechmea,

that's an interesting observation, as I also have lots of absorption in my room, but don't get much/any noticeable difference in the "quietness" of my room - likely due to having all the windows/doors always open for breeze in the Brisbane climate.

I've never regarded room treatment as being able to change the "isolation" of a room, only the "in room" sound, and leakage (in and out) will remain similar regardless of treatment???

 

cheers

Mike

Hi Mike,

We live on the edge of humanity; 1, 2 or 3 acre blocks in a long string so only 2 neighbours and they are over 100m away.  The only real source of external sound is the 110kph freeway (Pacific Highway, or whatever it is called now).  We can be thought of as country despite only being 3 minutes from Dan Murphys (every town's centre point).  The house itself is double brick which probably accounts for the "proofing" from the external highway noise.  There is no special construction other than normal thermal insulation in the roof.  The internal fibreglass treatment provides that extra eeriness when one walks into the room.  The room is at one end of the house well away from the living areas so not much interference from that.  Pretty happy with what I ended up with even if its not pretty.

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14 hours ago, almikel said:

My snoring annoys my wife more than me cranking the stereo :)

 

Reminds me of cheap ski trips decades ago with bunk rooms of 12 people. My brother (another snorer) and I would hand out ear plugs to the other bunk room occupants...I was never bothered by other snorers with ear plugs in...

...of course my wife can't put up with wearing ear plugs :(

 

Mike

While we are massively off topic and discussing sound measurements... :D

Have you ever tried to record someone snoring in your ear with your phone, thinking I've got a good sample this time, only to find when you go to play it back to her you can barely hear it? :D 

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I am most likely going to repeat something that has already been said here:

 

For isolation ensure that the room is decoupled from the rest of the building- for best results this means mounting the room on springs! so not practical for most but any connection  will transmit sound. Also as mentioned earlier (davewantsmoore, thankyou) avoid ANY gaps. A heavy weight construction works well but high quality acoustic fill can work (not the cheap stuff, try Autex). If possible ues diffent thicknesses of sheeting in and out of the walls. Also while you are at it don’t make the walls and ceiling parallel- there are articles on this out there - helps reduce standing wave issues. Once this is done then do wall treatments - absorbers, quadratics, traps as needed, cost there is up to no limit. Avoid foam products as they will disintegrate after several years and are messy!

 

Again apologies if I have repeated earlier valuable inputs

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16 minutes ago, smithc4w said:

I am most likely going to repeat something that has already been said here:

 

For isolation ensure that the room is decoupled from the rest of the building- for best results this means mounting the room on springs! so not practical for most but any connection  will transmit sound. Also as mentioned earlier (davewantsmoore, thankyou) avoid ANY gaps. A heavy weight construction works well but high quality acoustic fill can work (not the cheap stuff, try Autex). If possible ues diffent thicknesses of sheeting in and out of the walls. Also while you are at it don’t make the walls and ceiling parallel- there are articles on this out there - helps reduce standing wave issues. Once this is done then do wall treatments - absorbers, quadratics, traps as needed, cost there is up to no limit. Avoid foam products as they will disintegrate after several years and are messy!

 

Again apologies if I have repeated earlier valuable inputs

You touched on something not spoken about so far, and that is non parallel walls / ceiling floor. Since I will be building an inner room, I always planned to make the walls non parallel. If possible it would be nice to make the ceiling non parallel as well. Apparently and expanding room helps with standing waves.

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Somewhere I have information on room design using non parallel walls so I’ll see what I can dig up for you.

 

As for the room fitout I have used Aro Technology in SA for a Pro Tools editing suite and a Recording control room and that has been excellent in both cases (not cheap though!)

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4 minutes ago, smithc4w said:

Somewhere I have information on room design using non parallel walls so I’ll see what I can dig up for you.

 

As for the room fitout I have used Aro Technology in SA for a Pro Tools editing suite and a Recording control room and that has been excellent in both cases (not cheap though!)

Unfortunately most room calculators don't work on non parallel walls to model it properly, so it is one or the other.

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22 hours ago, Peter the Greek said:

Say you're targeting a 19db level, are the affordable meters capable of measuring that?

Doubt it.

 

My background noise level was down in the noise of the pro equipment my calibrator used.

 

Cheers,

Peter

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See Cardas.com for Golden Trapagon non parallel room dimensions, also his other information on room dimension ratios is interesting. Yes, cannot accurately model non parallel but modelling ain’t perfect - depends on how good the modeller is.

See photo for example of Aro Technology fitout, classical recording control room. This wasn’t perfect as it was built with a 2400 ceiling but got it to work pretty well. Also the back of the room was odd shaped - can’t see that in photo. Would have been better with the proposed 3000 ceiling of course.

IMG_0166.jpg

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4 hours ago, smithc4w said:

See Cardas.com for Golden Trapagon non parallel room dimensions, also his other information on room dimension ratios is interesting. Yes, cannot accurately model non parallel but modelling ain’t perfect - depends on how good the modeller is.

See photo for example of Aro Technology fitout, classical recording control room. This wasn’t perfect as it was built with a 2400 ceiling but got it to work pretty well. Also the back of the room was odd shaped - can’t see that in photo. Would have been better with the proposed 3000 ceiling of course.

 

 

Sweet! http://cardas.com/room_setup_golden_trapagon.php finally I can do it semi properly.

Ceiling height I am aiming for just around 4m. The home theatre room will sit somewhere between 1m - 2m below the carport level which will be around 2.4m The slope on the block (previous pages) allows the height difference.

I am also governed by a total height. I have to have a high pitched roof and I can only be a certain amount above ground level. I was hoping for 3m ceilings upstairs.

 

 

Edited by Silent Screamer
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For the added complexity/cost involved in building non-parallel walls IMHO it's not worth it...

I'm also very dubious of any benefit of so called "Golden Ratios" for room dimensions...

 

Just build the largest "decoupled" room possible avoiding even multiples for any dimension of length/width/height.

 

Do not reduce the size of your room to hit a "Golden Ratio" or incorporate non-parallel walls - sure increase the size of your room to hit a "Golden Ratio" - bigger is always better!

 

I think it was @Peter the Greek that said he'd prefer a larger cubic room over a smaller "any golden ratio you choose" room - I agree with this.

 

cheers

Mike

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Guest Peter the Greek
14 hours ago, almikel said:

I think it was @Peter the Greek that said he'd prefer a larger cubic room over a smaller "any golden ratio you choose" room - I agree with this.

 

100% - I suggest this for two reasons. The first is practical, building small rooms is PAINFUL. Trying to cram everything in is just crap, yes larger rooms cost more, but its so much easier to work and move around. This is especially try for true room in room builds, trying to get suspended ceiling joists into tight spaces can be a real hassle.

 

The second (and probably more important), once you start adding risers, stages, bulk heads, screen walls, cabinets etc etc the rooms quickly change shape. Any surplus space can be jammed full of bass trapping goodness to make it look neat - function and aesthetic.  

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17 hours ago, almikel said:

For the added complexity/cost involved in building non-parallel walls IMHO it's not worth it...

I'm also very dubious of any benefit of so called "Golden Ratios" for room dimensions...

 

Just build the largest "decoupled" room possible avoiding even multiples for any dimension of length/width/height.

 

Do not reduce the size of your room to hit a "Golden Ratio" or incorporate non-parallel walls - sure increase the size of your room to hit a "Golden Ratio" - bigger is always better!

 

I think it was @Peter the Greek that said he'd prefer a larger cubic room over a smaller "any golden ratio you choose" room - I agree with this.

 

cheers

Mike

Ordinarily I would be quick to agree with your thinking, but I think the room is bordering on being too big in some directions. at 6.8m wide inside the main wall, there is plenty of room to pinch some back for tapered walls. Even with the biggest of projector screens, I probably don't need the finished wall to be any more than 5m wide at the front.

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On 19/01/2019 at 2:24 PM, Silent Screamer said:

Apparently and expanding room helps with standing waves.

It does not work as well as human nature would predict it might.

 

For an example.    let's say you have a room which gets wider as you go from front to back.   It's 4m wide at the front, and 5m wide at the back.

 

If you look at the primary width mode, it is 43Hz where the room is 4m wide... and 34Hz where the room is 5m wide.    There isn't a lot of difference.

 

At higher frequencies the reflections from the side walls will be different (due to the angle) ..... but this doesn't necessarily mean better.... and there are other ways to modify those reflections (eg. by moving the speaker and/or the listener)

 

 

It is the same with "golden ratio" room dimensions.

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3 minutes ago, davewantsmoore said:

It does not work as well as human nature would predict it might.

 

For an example.    let's say you have a room which gets wider as you go from front to back.   It's 4m wide at the front, and 5m wide at the back.

 

If you look at the primary width mode, it is 43Hz where the room is 4m wide... and 34Hz where the room is 5m wide.    There isn't a lot of difference.

 

At higher frequencies the reflections from the side walls will be different (due to the angle) ..... but this doesn't necessarily mean better.... and there are other ways to modify those reflections (eg. by moving the speaker and/or the listener)

 

 

It is the same with "golden ratio" room dimensions.

I have seen similar written before that while a lot of it is good in theory, the real world application often doesn't meet expectations. I guess it comes down to do the best you can without increasing the cost so dramatically that it outweighs any benefit you might get from it.

 

If option allows common sense dictates that you don't build a perfect cube room because it has the worst possible room modes. Sometimes we might be dealing with less than ideal but it is what we have to work with. Fortunately having a clean slate to work with I do have options, but I need to be mindful of the cost to any benefit to be gained.

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On 19/01/2019 at 11:25 PM, Silent Screamer said:

Sweet! http://cardas.com/room_setup_golden_trapagon.php finally I can do it semi properly.

What they say is true

Quote

The Golden Cuboid (Diagram H) is the best "rectangular" shape for a listening room.

.... what they don't tell you is how close in performance many(!) room dimensions are.

 

 

They make it sound like as you zero in on the golden dimensions that the performance improvements will come...... when in reality it is as you move away from the very problematic dimensions the performance improvements will come .... and as you go close and closer to "golden dimensions" the performance improvements will slow/stop.

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1 minute ago, davewantsmoore said:

What they say is true

.... what they don't tell you is how close in performance many(!) room dimensions are.

 

 

They make it sound like as you zero in on the golden dimensions that the performance improvements will come...... when in reality it is as you move away from the very problematic dimensions the performance improvements will come .... and as you go close and closer to "golden dimensions" the performance improvements will slow/stop.

I have actually seen quite a number of alternate ratios listed on the web, some for listening, some for movies, even ones claiming to be for THX.

In what why do you consider them problematic? Aren't they called the golden ratio because they are mathematically the perfect ratio?

 

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