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window behind monitors.... best way to treat this??

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Re: window behind monitors.... best way to treat this??

Postby Ethan Winer » Mon Jan 03, 2005 9:27 pm

0,

> the second part of that response is just patronising and rude <

That was not the intent. But I already explained it six ways to Sunday. If he can't - or won't - understand, that's not my fault. This is not a complicated concept!

As for rudeness, I noticed that yet again you had to edit someone else's post repeatedly. So why single me out rather than that other person?

> as Eric had already explained and has again, the absorption, transmission and reflection properties of a window are related. Yes, they all describe different parts of the mechanical behaviour of the window but they are all physically related. <

No disagreement there. I came to the realization on my own years ago that all materials pass, absorb, and reflect, all at the same time.

We can argue about this forever, but until someone posts some hard data to show how much less a window reflects than a sheet rock wall, this will continue indefinitely. I'd have thought that Eric would have such data handy. I found some graphs that were close, but not exact, in about five minutes on Google.

It should be obvious, intuitively, to all that a window reflects bass frequencies less than a solid wall. How much less I can't say for sure because I never measured that. But I did already make the point that reducing a reflection even a little reduces the severity of the resulting acoustic null by a much larger amount. Even a 1 dB reduction in the strength of a reflection reduces the depth of a null by many dB.

Since nobody else is offering any data I'll go first. Here are some hard numbers on the relative significance of a reflection:

    If a reflection is 100 percent it will create a null of infinite depth 1/4 wavelength away from the boundary.

    If you reduce the reflection by 1 dB the null is now only 19 dB deep.

    Reduce it another dB and now the null is only 14 dB deep.

    Reduce it again to -3 dB and now the null is only 11 dB deep.

    If you reduce it to -6 dB the null is now only 6 dB deep.

So if glass reflects, say, 40 Hz at -6 dB compared to -1 dB for sheet rock, that alone accounts for a huge improvement in the LF response inside the room. Depending on how much of the entire wall is glass, of course.

--Ethan
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Re: window behind monitors.... best way to treat this??

Postby Ido » Mon Jan 03, 2005 10:43 pm

Ethan,
From your posts, it is apparent you chose to ignore the full context of what I said, rather you picked something out of context to which you answered same thing over (which I managed to digest the first time, believe me).

My main point was:
What is the practical significance of what you say,
how does it influence the necessity (or not) for inner room treatment?
Either you need treatment (absorption), or you don’t.
The window’s (or any partition’s) acoustic characteristics are a GIVEN.
(The door to the room might absorb just as much as this poor window, so what?)
I think we all want to make things clear and helpful, as opposed to vague and potentially misleading.

I would appreciate you're addressal of these previous quotations (from myself):

..I think some misunderstandings might arise in certain settings (as in Doezer’s), to the effect of:
“hey, I’m not sure about this window thing, I think I might need to treat & absorb it, but then again, it might do some good for the bass. na, I’ll leave it be”.
Now please, I don’t want to argue, nor get into mechanisim disscussions. I want to keep it simple and straightforward for those who might be confused, so kindly hear me out, maybe we will all agree on the following:

1. It is preferabe to separate the inner acoustic treatment (mainly absorption) from noise isolation considerations. What I mean with this is that if you have an inner acoustic problem, treat it accordingly, and don’t rely on possible non-direct mechanisms stemming from isolation or others. I would only “rely” on such if I assuredly knew en-field that it works, that the problems are solved, and that no acoustic compromises are made...




And this, from which you selectively quoted me out of context ..


1. I honestly don’t understand why you keep on with “LF energy passing through window” motif. It is very vague (“.. passes some of that energy..”), so that I fail to see any practical implication from it in this case:
If the specific window area creates reflections that need be treated, you treat them. If not, you don’t treat them.
If you’re not sure (which is common), take some absorbent of any kind, cover the window, and hear/measure if there is a difference/improvement.
If not, obviously no treatment is necessary.
If there is some difference, and you want the window visible, do the curtain.
How does the window’s “LF energy passing” as you call it, change this?



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Re: window behind monitors.... best way to treat this??

Postby Ethan Winer » Tue Jan 04, 2005 12:12 am

Ido,

> it is apparent you chose to ignore the full context of what I said <

That really was not my intent.

> What is the practical significance of what you say, how does it influence the necessity (or not) for inner room treatment? <

The numbers I posted above show how reducing the level of an interfering reflection by even 1 or 2 dB can significantly reduce the depth of nulls inside the room. This has been my point all along. If a window passes lows to the outside a little more than a sheet rock wall passes lows, then there's less reflection and therefore less acoustic interference inside the room.

Okay?

--Ethan
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Re: window behind monitors.... best way to treat this??

Postby Scott R. Foster » Tue Jan 04, 2005 9:29 am

No.

The window described is not an absorber by any stretch of the rational meaning of this term in context.

Nor it is an effective low pass filter with a "crossover frequency".

Nor will its "passing" of energy to the outside "move nulls" around.

I have no quarrel with you [or anyone else] questioning DZ's proposition of treating the window with an absorptive overlay, particularly if he wants to look out of it later... BUT pretending you can predict beneficial acoustic artifacts in DZ's room that will arise from retaining the subject window [which BTW is of unknown properties] is ridiculous, and your "scientific" thoughts on the matter - collectively - don't hold water.

On this topic - It seems to me you are not grasping the energy levels involved, nor are you "getting it" in terms of the interaction of physical properties which would define the results, nor are you understanding that a rattling window pane is introducing a new set of vibrations back into the room [defined by its physical properties].

Meanwhile... I'm wondering what DZ did with his room... we may never know. I hope he found a better resource than this thread for making a decision on how to treat his window... as this thread has become a broken pencil.

Pointless.

:headbang:
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Re: window behind monitors.... best way to treat this??

Postby Hugh Robjohns » Tue Jan 04, 2005 11:10 am

Jeez! I go away for a couple days rest and relaxation and come back to find everyone still trying to rip each other's throats out! I'm also very disappointed that 0VU felt it necessary to edit Eric's post so heavily. :roll:

Foz wrote:The window described is not an absorber by any stretch of the rational meaning of this term in context.

I thought we had already ALL agreed that.

Nor it is an effective low pass filter with a "crossover frequency".

An 'effective LPF'? I think we'd all agree that too, although it rather depends on how you define the term 'effective'.

Nor will its "passing" of energy to the outside "move nulls" around.

No one has ever suggested it will MOVE the positions of nulls. However, it has been suggested that by reducing the amount of energy reflected internally, the depth of a null can be decreased, thus producing a slightly less 'peaky' overall response in the room. This could be considered a positive advantage, contributing in some small way to the overall goal of the rest of the LF acoustic treatment.

...pretending you can predict beneficial acoustic artifacts in DZ's room that will arise from retaining the subject window [which BTW is of unknown properties] is ridiculous.

I wasn't aware that anyone had predicted any specific benefits. All that was suggested was that leaving the window where it was and untreated was very unlikely to create any significant additional LF acoustic problems.

I hope he found a better resource than this thread for making a decision on how to treat his window... as this thread has become a broken pencil.

I thought he had all the constructive advice he needed within the first couple of posts. Like you, I hope he has dealt with the issue and moved on to something musically productive in his new room.

Hugh
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Re: window behind monitors.... best way to treat this??

Postby DoeZer » Tue Jan 04, 2005 11:14 am

hi y'all

i just wrote a lengthy response to all your responses and included extra info on my room , then clicked submit but it never made it!!! :x :x :x

sorry but i cant bring myself to type it all again right now! :x.

will do later!

D
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Re: window behind monitors.... best way to treat this??

Postby DoeZer » Tue Jan 04, 2005 12:01 pm

Hi.
again!!!
well it sems Ive sparked off quite a debate again!

anyway, Im just gonna post with some additional info on my room. The situation is this.

I have a room of 10'7" x 7'8" x 7'9". unfortunately a 1-1 ratio between width and height but hey thats life...


the room is on the side of the house so theres no room above it and no neighbours to the side either so thats good!
The four walls are conctrete, two of them outer walls (thicker) and two of them internal (so only 4!" blocks, still should be good for retention right?)
They all had battens with standard insulation on them
but i did a sound-check by putting a radio in the room and listening in the kitchen next door to the sound and the noise retention was, as expected, crap.

SO!!! my plan is this. I have already stripped the walls bare and will now put 4x2 battens with 60kg/m3 rocksil insulation in between them and then cover with a layer of plasterboard. I will get a new door made which will be like a standard house door but with the following changes... some rocksil wool placed in between the two door faces, there will be a neoprene seal all round at closure and i'll put a compression latch on it also. But its NOT gonna be a double door. I dont have the time/money to get into all of that.

in answer to your question OVU, the answer is yes to all of your assumptions :). i do want to get a good soundproofing and sound response within the room but within a reasonable budget and im willing to make some compromises. this isnt a commercial venture but i do want to get as 'true' a sound environment in there as possible... :).

so as for the window, its in the front of the room and is about 4 foot wide.... reading all of the responses i'm reckoning that i will put heavy curtains or a shutter in to reduce HF reflections and that would be a solution more in keeping with the level of design of the rest of the room, i.e. wont be "Sun Studios" but should be OK...

I am going to have more posts on all of this over the next week or so because all of a sudden everythuing is happening and Ive a builder in the house working on other stuff who'll be ready to work on this room very soon indeed..:shock: :shock: :shock: .....

thanks
D
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Re: window behind monitors.... best way to treat this??

Postby DoeZer » Tue Jan 04, 2005 12:29 pm

oh yes.

one more thing...

I dont plan to take the plasterboard ceiling down and put rosksil above it and replace it with new plasterboard. i know this would improve sound retention but above it theres nothing! so i dont really mind if there's less retention there... does this seem reasonable???

cheers

D
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Re: window behind monitors.... best way to treat this??

Postby Scott R. Foster » Tue Jan 04, 2005 8:30 pm

DZ:

Your TL to the rest of the house will be no better than your weakest link... if you have only a thin ceiling then sound intrusion to the balance of the building will be defined by that barrier regardless of how well you do the walls and door. You might consider at least adding a layer of plasterboard to your exiting ceiling. Double thick insulation batts in the attic over the sound room wouldn't hurt either.

Your door is probably also a weak link as you surmise... and pre-made high TL doors are expensive [its a niche product] so making a door yourself as you propose is probably a great solution... in any event, it is a solution that has worked well for many... see Paul's studio build diary for a good example.... though given your wimpy ceiling, going as far as Paul did probably doesn't make sense.

Adding additional mass to the door you are building may be a better proposition than the mineral fiber stuffing you describe. An old school trick is to make the door from several layers of dense panels [like 3/4" MDF for example] and step the size of the panels so the edge is stair cased along the sides and top. Make similar steps in the door jamb so the door and jam overlay each other more than once... like the door of a safe

Image

With a stepped profile you can add multiple seals along the sides and top... then add a double sweep for the threshold. Generally the seals on the door are the key... bad seal = leaky door... when the seals wear out the door stops working as an effective acoustic barrier.

Even a lightweight door can exhibit stunning improvement by simply adding good seals. Some folks have met modest needs by simply adding mass [a panel of MDF] and good seals to an existing door.

Also, I have had good luck hanging two doors in the same frame [one opens in, and the other opens out]... with good seals this two doors in one hole design can be amazingly effective.

Compression latches are good way to go, but if you get the fit right you can use a simple magnetic latch... or magnetic seals [like a refrigerator door] and no latch.

Good Luck!
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Re: window behind monitors.... best way to treat this??

Postby Scott R. Foster » Tue Jan 04, 2005 8:37 pm

DZ:

Just to be clear... do you have an attic that connects the space above your room to the balance of the home?
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Re: window behind monitors.... best way to treat this??

Postby Paul Woodlock » Tue Jan 04, 2005 9:53 pm

Foz wrote:DZ:
.....so making a door yourself as you propose is probably a great solution... in any event, it is a solution that has worked well for many... see Paul's studio build diary for a good example.... though given your wimpy ceiling, going as far as Paul did probably doesn't make sense.

Foz gives good advice :)

My doors are FIVE Layers of 18mm MDF and 1 layer of 15mm plasterboard snadwiched inbetween,and built bank vault style, as Foz describes below....


Adding additional mass to the door you are building may be a better proposition than the mineral fiber stuffing you describe. An old school trick is to make the door from several layers of dense panels [like 3/4" MDF for example] and step the size of the panels so the edge is stair cased along the sides and top. Make similar steps in the door jamb so the door and jam overlay each other more than once... like the door of a safe

Image

With a stepped profile you can add multiple seals along the sides and top... then add a double sweep for the threshold. Generally the seals on the door are the key... bad seal = leaky door... when the seals wear out the door stops working as an effective acoustic barrier.

... and yep, the seals are very important. I used a double seal all the way around ( the threshold was 'bank vault' too ) of 1/2 round neoprene seal ( supplier at end of message ).

Although the TL of the two doors is excellent, and I'm more than happy, I do need to 'tweak' the door jambs a tad to get the seals to an exact fit, as their is still some leakage. nto a big problem, and one which I'll tackle towards the end of the studio build.






Compression latches are good way to go, but if you get the fit right you can use a simple magnetic latch... or magnetic seals [like a refrigerator door] and no latch.

Good Luck!

I got my compression latches for abut £15 each. They're made by EMKA, and I got them from the UK distributer. I think they were called FA Parkes ltd ( Do a google for EMKA ), Highly recommended, great service.

I got the neoprene 1/2 round seal from Siderise Ltd. It was about £1/m. However I can't recommend Siderise Ltd, as the bastards charged me £25 (!!! :frown: ) for postage and packing. And postage and packing was merely a 2nd hand cardboard box and a couple of quid postage. So for this... Siderise Ltd are NAMED and SHAMED!!!! :)

Paul
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Re: window behind monitors.... best way to treat this??

Postby DoeZer » Wed Jan 05, 2005 9:51 am

this is great stuff guys. very useful. thanks....

I wont get to the door side of things for a couple of weeks but will refer back to this when i do... it doesnt sound that difficult to do either (famous last words ;)).

@ Foz

Im afraid regarding the ceiling Its not as simple as I'd like....

This room is on the ground floor with nothing above it except a pitched slate roof slanting up to the side wall of the house - i.e. its on a a 'wing' of the house which has a converted garage (already needed for something else) and at the back of that there is this room. do you get my drift??

SO there is not attic entrance, no way of adding insulation above the plasterboard - if i could i would... Yes i could remove the plastebroard completely and make a much bigger room volume out of it but to be honest I cant do that at the moment. Im too busy with other stuff to get into it and it'll have to be a 'down the line' thing, maybe next year :). I will add an extra layer of plasterboard though (is it best to put some kind of layer in between the two plasterboard layers?)

BUT my thought was, from a sound isolation point of view, who cares if the ceiling is not absorbing as much sound. Above it there's only sky (hey hang on I think I feel a song coming on ;))... and theres no way the people in the rest of the house will hear this sound.

btw thanks for your answer on the insulation in the other post, i'll order that today.

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Re: window behind monitors.... best way to treat this??

Postby Doublehelix » Wed Jan 05, 2005 2:26 pm

Ya know, after the last flame war fiaso, I decided to stay away from the SD&A forum for a while.

I come back, and nothing has changed!!!

It is the same combatants fighting over the same childish crap.

While I respect the knowledge of Ethan, Eric, Paul, Foz, etc., all this petty bickering is so damn frustrating! The only ones left reading the thread are the ones doing the arguing!!! Take it somewhere else!

It is sooooo obvious to anyone on the outside-looking-in that you guys all have a personal agenda, and can't wait to prove each other wrong, and to prove how great you are, when you really have very little desire to help the original poster. (At least it seems that way to me)

Arguing over semantics, and getting into a technical bees-hive does nothing to answer the question of the average musician or studio owner. This place is filled with recording musicians that don't really give a crap about acoutic theory, but just want their rooms to sound good so they can get back to making music.

I understand the need to be somewhat technical, so that some of the "hows" are backed up with some "whys", but sheesh guys! Give it a rest.

:round1:

Pathetic really...
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Re: window behind monitors.... best way to treat this??

Postby Scott R. Foster » Wed Jan 05, 2005 4:39 pm

DZ:

Maybe draw a sketch of how the roof / ceiling works to define the space above the room and how the space above the ceiling connects to the balance of the house / attic [if it does]?

I do not think I would add a gap to an extra layer of plasterboard... I'd just add it flat to the existing [easiest way to add mass]... but I'd like to know more about what you have got. Are you confident the ceiling joists will hold more weight? Are you confident more ceiling layers will help TL to the balance of the building [see question above]?

Maybe do the door first and then see what you got? Identify the weakest links and work those first... are you sure your walls need additional TL? Are they masonry? If so you may be best off focusing on the door / ceiling / duct work.

A rubber tube in your ear to a small pipe will let you zoom in on sound leaks - Put a loud source with lots of LF content in the room... shut it up tight... and check around door seals, HVAC ducting, electrical outlets, the ceiling and walls of adjacent rooms. Be sure to wear a tin foil hat too in case the neighbors see ya so you can tell you them are looking for your alien flea band that has got out of its cage.... that oughta shut em up for a couple of days.
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Re: window behind monitors.... best way to treat this??

Postby thefruitfarmer » Thu Jan 06, 2005 10:24 am

Foz wrote:

A rubber tube in your ear to a small pipe will let you zoom in on sound leaks - Put a loud source with lots of LF content in the room... shut it up tight... and check around door seals, HVAC ducting, electrical outlets, the ceiling and walls of adjacent rooms. Be sure to wear a tin foil hat too in case the neighbors see ya so you can tell you them are looking for your alien flea band that has got out of its cage.... that oughta shut em up for a couple of days.


:bouncy:

Even a small hole will let through a lot of sound; I can't explain exactly why this is the case but it does. I could have used the rubber pipe in the ear trick a few years ago when I made a sound insulating floor.
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