Studio Walls - Insulating, Covering & Sloping

[Ethan Winer]

Carpet is a poor choice because it absorbs only high frequencies. Absorption should work over as wide a range as possible, so rigid fiberglass or even foam is a much better choice.

Angling the walls and ceiling scan help in some situations, but only if the angles (and room) are fairly large. How big is your space?

I don't have direct experience with cellulose, but plain fluffy fiberglass inside walls works very well.

--Ethan

The Acoustic Treatment Experts

[PaulInTheSticks]

Hi Ethan,

Thanks for the info.

I've got some rigid mineral wool panels to put up on the walls but I was referring to something to go over the studs to cover the entire walls. I assume carpet would be alot better than drywall, wood or any other hard covering?

My tracking room is only 9 x 11 and I've got a steep peaked ceiling. Sounds like I should skip the angled walls. It would be a hassle any way and this is a project studio.

Originally Posted by Ethan Winer

Carpet is a poor choice because it absorbs only high frequencies. Absorption should work over as wide a range as possible, so rigid fiberglass or even foam is a much better choice.

Angling the walls and ceiling scan help in some situations, but only if the angles (and room) are fairly large. How big is your space?

I don't have direct experience with cellulose, but plain fluffy fiberglass inside walls works very well.

--Ethan

The Acoustic Treatment Experts

[Ethan Winer]

You mean carpet instead of drywall? That would be good acoustically, but it probably won't pass muster with the fire Marshall.

--Ethan

[PaulInTheSticks]

Originally Posted by Ethan Winer

You mean carpet instead of drywall? That would be good acoustically, but it probably won't pass muster with the fire Marshall.

Yes carpet instead of drywall. Fire Marshall? What Fire Marshall? I live in the middle of nowhere. Didn't even have to get permits to build my house.

[gullfo]

i think this is a duplicate of the "cheap wall covering" thread. carpeting the walls is generally bad acoustically and a potential fire hazard.

[PaulInTheSticks]

Ethan,

For comparing the soundproofing affect of cellulose vs fiberglass, there is no comparison. Check out this video: Cellulose vs. FIberglass Insulation Sound Proofing Demonstration - YouTube

[GIK Acoustics]

Originally Posted by PaulInTheSticks

Yes carpet instead of drywall. Fire Marshall? What Fire Marshall? I live in the middle of nowhere. Didn't even have to get permits to build my house.

The fire marshall exists for a reason - and that is to point out unsafe building methods to ensure lives aren't endangered. I already posted in the other thread but I will add a bit about your angled walls question.

A 12 degree minimum angle (so 6 degree per wall) is suggested to break up flutter echo. A much stronger angle is needed to break up standing waves and some modal behavior. I've seen some quote around 30 degrees for this. However, with an overly dampened room you wouldn't really gain a lot (since you will have no flutter echo) unless they were heavily angled to break up modal activity.

[Rod Gervais]

Originally Posted by PaulInTheSticks

Ethan,

For comparing the soundproofing affect of cellulose vs fiberglass, there is no comparison.

The test you linked to is meaningless.

The only thing that's meaningful is a lab test using comparable wall construction.

Probably the most extensive testing done on isolating assemblies were those performed by the National Research Council Canada (NRC)

In their publication IR-761 they tested over 350 wall assemblies - and they did this strictly for the data - not to promote any particular product - so this is as unbiased a set of results as you will ever find.

In their tests numbered TL-93-313 (sprayed cellulose insulation) and TL-93-283 (fiberglass insulation) you can compare 2 otherwise identical wall assemblies - 2x4 framing - 24" on center - 1" air space between inside faces of framing double layers of 5/8" type X drywall on each face - wall samples were 8' high by 10' wide.

Here's the results (TL values for the sprayed cellulose are the ones on the left):

TL-93-313(STC 66) TL-93-283 (STC 69)

Frequency...TL........TL
50 Hz.......30.0......26.7
63 Hz.......21.0......31.8
80 Hz.......28.8......36.6
100 Hz......37.0.....39.5
125 Hz......44.4.....44.6
160 Hz......48.3.....51.3
200 Hz......51.9.....55.9
250 Hz......55.7.....61.8
315 Hz......57.2.....64.9
400 Hz......60.3.....67.3
500 Hz......64.8.....70.1
630 Hz......67.2.....72.9
800 Hz......71.3.....78.0
1000 Hz....75.3.....81.5
1250 Hz....79.8.....85.6
1600 Hz....81.4.....83.9
2000 Hz....75.5.....75.3
2500 Hz....75.5.....75.9
3150 Hz....82.1.....81.7
4000 Hz....88.1.....87.4
5000 Hz....92.2.....91.5
6300 Hz....91.1.....90.7

Now - the overall advantage lies with fluffy fiberglass insulation in this case - sure you get a small boost with cellulose at 50Hz (3.3dB) but then take a huge hit in isolation at 63Hz (-10.8dB).

When you look at the numbers as a whole - it simply makes no sense whatsoever to bother with anything other then the cheapest material you can put in the bay - which is fiberglass.

If you wish I could post the same comparison for fiberglass versus blown cellulose insulation - but I'll let you know in advance that I used spray cellulose right off the bat because it performed better then the blown did in the comparison.

I would also point out that there has to be some concern with blown as to the possibility of it settling over time - as it does the TL values will decrease, perhaps dramatically.

According to the video you linked to - there would be a clear advantage to making use of cellulose of roughly 33dB weighted - that is huge - yet we don't see it when we look at real world test results (in fact we see a 3dB weighted benefit to the fiberglass).

You can (of course) use whatever you wish to use - perhaps "green" is your motivating factor - in which case go green and settle for less isolation over all - there is nothing wrong with that if that is your choice - but don't buy into the bullshit hype you find on you-tube - at least use real data to base the decision on.

Rod

[spectrasound]

Thanks Rod...for the real data!

[Ted White]

Yes, thanks Rod. These meaningless comparisons get old after a while.

[Rod Gervais]

Guys,

Sometimes even lab numbers have to be looked at hard......

I had a cellulose company bid on a high rise hotel project I did once - insulation of outside walls and isolation between guest rooms - I told the construction manager running the project that we would not pay more for cellulose than fiberglass......

So this guy shows up at my office from the company bidding and begins explaining to me that their product beat FG hands down when it came to isolation.

I asked for a copy of the lab tests - and he produces a typical printout of the results from their product test.

I explain to him that it's meaningless - the only thing I will accept would be the full copy of the original test report they pulled that data from.

So he shows up a couple of days later with the report - and, after I look at it, I smile and said the numbers were (apparently deliberately) skewed because of the manner in which the test was done.

I pull out IR-761 - flip to the page that is their product tested in our configuration and ask him to compare the numbers between the 2 test results - which apparently amazed him..... and when he said that he could not understand why the numbers were so different I told him to look at the sample sizes from each test.

IR 761 used those 8' tall by 10' wide samples in their tests - and in the one his company did the sample was only 4' wide.

the 10' wide sample with multiple seams in the field is more representative of the real world - their sample was more representative of a wall in a closet.....

You'll always get a slight improvement when the only thing you have to worry about are edges and not multiple joints in the body of the wall.

He walked away - without the project - but at least he understood why I was not willing to pay a premium for their product.

Rod

[Ted White]

That's a great story Rod. Very appropriate

[PaulInTheSticks]

Rod, thanks for the data.

In this testing, I assume the fiberglass was in batts? Also, was it faced or unfaced?

Originally Posted by Rod Gervais

The test you linked to is meaningless.

The only thing that's meaningful is a lab test using comparable wall construction.

Probably the most extensive testing done on isolating assemblies were those performed by the National Research Council Canada (NRC)

In their publication IR-761 they tested over 350 wall assemblies - and they did this strictly for the data - not to promote any particular product - so this is as unbiased a set of results as you will ever find.

In their tests numbered TL-93-313 (sprayed cellulose insulation) and TL-93-283 (fiberglass insulation) you can compare 2 otherwise identical wall assemblies - 2x4 framing - 24" on center - 1" air space between inside faces of framing double layers of 5/8" type X drywall on each face - wall samples were 8' high by 10' wide.

Here's the results (TL values for the sprayed cellulose are the ones on the left):

TL-93-313(STC 66) TL-93-283 (STC 69)

Frequency...TL........TL
50 Hz.......30.0......26.7
63 Hz.......21.0......31.8
80 Hz.......28.8......36.6
100 Hz......37.0.....39.5
125 Hz......44.4.....44.6
160 Hz......48.3.....51.3
200 Hz......51.9.....55.9
250 Hz......55.7.....61.8
315 Hz......57.2.....64.9
400 Hz......60.3.....67.3
500 Hz......64.8.....70.1
630 Hz......67.2.....72.9
800 Hz......71.3.....78.0
1000 Hz....75.3.....81.5
1250 Hz....79.8.....85.6
1600 Hz....81.4.....83.9
2000 Hz....75.5.....75.3
2500 Hz....75.5.....75.9
3150 Hz....82.1.....81.7
4000 Hz....88.1.....87.4
5000 Hz....92.2.....91.5
6300 Hz....91.1.....90.7

Now - the overall advantage lies with fluffy fiberglass insulation in this case - sure you get a small boost with cellulose at 50Hz (3.3dB) but then take a huge hit in isolation at 63Hz (-10.8dB).

When you look at the numbers as a whole - it simply makes no sense whatsoever to bother with anything other then the cheapest material you can put in the bay - which is fiberglass.

If you wish I could post the same comparison for fiberglass versus blown cellulose insulation - but I'll let you know in advance that I used spray cellulose right off the bat because it performed better then the blown did in the comparison.

I would also point out that there has to be some concern with blown as to the possibility of it settling over time - as it does the TL values will decrease, perhaps dramatically.

According to the video you linked to - there would be a clear advantage to making use of cellulose of roughly 33dB weighted - that is huge - yet we don't see it when we look at real world test results (in fact we see a 3dB weighted benefit to the fiberglass).

You can (of course) use whatever you wish to use - perhaps "green" is your motivating factor - in which case go green and settle for less isolation over all - there is nothing wrong with that if that is your choice - but don't buy into the bullshit hype you find on you-tube - at least use real data to base the decision on.

Rod

[Ted White]

Any open fiber insulation of similar density will perform similarly.

Out of the 4 elements of soundproofing, absorption (insulation) does the least, so I wouldn't spend too much time on it.

[leafthelucky]

I'm a new suscriber here, and I'm here to learn as much as I can. I too was thinking about using cellulose to make sound treatment panels for a listening room in my home. Sprayed cellulose insulation (6" thick) stopped sound so well that I literally could not hear someone talking 10 feet away. A "rough-framed" home that I was working in had no windows or doors installed; it had exterior sheeting and cellulose. As long as I kept "line of sight" through a window opening, I could hear my Uncle giving instruction, or the fork lift putting up trusses. Move away from the window behind the cellulose and it was QUIET. Almost erie, really. I found a company that makes a product called ECOCELL, which are 4'x8' sheets of 3.5" thick cellulose,for about $36 a sheet. I wanted to try the cellulose batt cut to 2'x4' for first reflection panels and for 24"x17"x17" corner bass traps stacked to the ceiling. Rod, please correct me if my logic is flawed, but dense-pak cellulose batt 2'x4' seems almost the perfect stuff for first reflection panels and corner bass traps. I could double them up (7" thick) for "Monster"bass traps. I'll build them; if anyone would like to test them, feel free to do so. I love a good experiment! Anybody with test equipment live in Michigan?