Isolation wall without rockwool (bass blocking)

[spitzer]

A room. Three walls are thick concrete/plaster/brick.

The "door" or "fourth wall". How to prevent low, including very low (under 100 Hz), frequency sound from getting through?

Rockwool, fiberglass and similar materials only absorb or block high frequencies, so why would one use them at all as part of the construction? I've read somewhere that the blocking effect of drywall or fiberboard decreases with every consecutive layer, however frequencies are seldom mentioned in that context.

I would assume that 10 layers of fiberboard would block low frequencies more effectively than 2 layers of fiberboard and whatever thickness of rockwool behind it (air gap or not, your choice). Right or wrong?

 

[rob aylestone]

Fibreboard is pretty unbalanced as an absorber - same with rock wool. HF gets attenuated more. They more mass in the walls you can get in my own practical experience makes a difference. An extra 18mm of plasterboard is better at preventing bass leakage than stuffing the gap with anything.

You seem to want precise data and evidence. Why would anyone use 10 layers of fibreboard. In the UK, it's normally 9.5mm thickness, so that's pretty close to 100mm rockwool. Rockwool is more dense per cu/m than fibreboard, so the physics suggests it would perform better, lower in frequency.

There's also reflections to consider, so an empty cavity will reflect back from the far wall. Rockwool, fibreglass and even 10 sheets of insulation board will diffuse the reflections. I'm not impressed with insulation board to do anything other than provide isolation and a previous studio was certainly warmer for longer when there was player of insulation board in the wall and ceiling. It didn't perform better though from an audio perspective, so thermal performance was the only benefit I could quantify. Two people can speak perfectly well through insulation board.

If you want absolutes then go to the suppliers and ask for the attenuation figures at key frequencies - then you have your facts.

 

[miroslav]

What is "fiberboard" exactly...since you guys sometimes have different terms for some materials we use here in the USA...I just want to understand what it is we are talking about?

I agree that "10 layers" of anything is denser than 2 layers...but with some things, there's the reality check that makes 10 layers undoable.

It takes a lot to stop and/or absorb very LF...so mass and density are key, and a combination of both fiberglass/rockwool and drywall/plasterboard of a few layers rather than 10 layers and no insulation, is the better solution.

Also...if you just have drywall on an empty stud wall, the possibility of LF resonance in the wall is very real. Having insulation in the wall will reduce/remove that.
That's why with my current studio build, I told them I wanted full insulation and the double drywall also on the "4th wall", which is an inside wall, and with normal construction procedures, would not get any insulation....though these days, many new builds include it, or people ask for it, because of the noise reduction you get by having insulation even between inside walls.

Look...you want proven answer to proper studio construction techniques and materials...go pick up the Rod Gervais book on studio construction, "Home Recording Studio, Build it Like the Pros".

There is a lot of overkill information there...so that you CAN build 100% like a commercial pro studio, if that is your desire and your budget allows it...but you don't need to use ever technique in the book, though you can glean a lot of useful information that could apply to your particular situation....and most of all, it only gives applicable information.
IOW...if some material or technique is not mentioned, you can probably not worry about...unless you're one of those people who needs to prove everything to yourself, even if it's already been proven many times over...in which case, just go with the "trial and error" approach if you don't just want to believe and accept what's already been demonstrated.

One of the key points made in the book by the author...is that you have to first ask yourself what are you after...what is your goal....like, do you need 100% soundproofing, or is that not an issue. IOW...you're not worried about sounds going in/out, but you're more interested in the quality of the sound you have in the studio. So then, no need to obsess over some over-the-top isolation build, if that's not really needed in your situation.

I'm always surprised with home studio builds how often people are overly focused on "soundproofing"...iso-booths and all that...but not so much on the quality of the sound. I can only assume that many are working mostly ITB, so they don't care about good room sound...though of course, unless you then mix entirely with cans, the room is still part of the equation. Anyway...I'm not sure why soundproofing is such a bid thing for most home studios...and the reality is that home studios often are hardest to achieve soundproofing because most houses were never build with that in mind...and you pretty much need a "ground up" build for 100% soundproofing.

 

[spitzer]

Fibreboard is pretty unbalanced as an absorber - same with rock wool. HF gets attenuated more. They more mass in the walls you can get in my own practical experience makes a difference. An extra 18mm of plasterboard is better at preventing bass leakage than stuffing the gap with anything.

You seem to want precise data and evidence. Why would anyone use 10 layers of fibreboard. In the UK, it's normally 9.5mm thickness, so that's pretty close to 100mm rockwool. Rockwool is more dense per cu/m than fibreboard, so the physics suggests it would perform better, lower in frequency.

More mass is exactly what I was going for. A massive, THICK wall should stop low freq more than a thinner and lighter wall with something soft (and light) like rockwool batts behind it, should it not? I'm a bit confused by how you said in the first paragraph that more mass is better, but contradicted that in the next paragraph, referring to density? Which one is it? Mass or density?

No need for "precise data and evidence". What am I, a cop?

There's also reflections to consider, so an empty cavity will reflect back from the far wall. Rockwool, fibreglass and even 10 sheets of insulation board will diffuse the reflections. I'm not impressed with insulation board to do anything other than provide isolation and a previous studio was certainly warmer for longer when there was player of insulation board in the wall and ceiling. It didn't perform better though from an audio perspective, so thermal performance was the only benefit I could quantify. Two people can speak perfectly well through insulation board.

If you want absolutes then go to the suppliers and ask for the attenuation figures at key frequencies - then you have your facts.

What empty cavity?

 

[miroslav]

Oh...if you have so much mass/density to effectively block all LF...well then you have to ask yourself, where is all the LF energy going to go if it's not absorbed.
So then, you have to substantially increase LF absorption in the room...which is a major PITA.

Ideally, if the LF is somewhat blocked AND also absorbed by the walls...then you don't need to add tons of LF absorption in the room.
If anything...you would want the LF to pass out and not come back. So just blocking, creates new issues.

 

[spitzer]

Oh yeah, sorry. Fiberboard in this case would be "low density particleboard". Although indeed it doesn't really matter, could be MDF, drywall or... cast iron, in any case 10 layers (with the typical ~2 cm board thickness) is 10 layers. A quick check told me that the cheapest particle board they sell is 700 kg/m^3... and rockwool batts are around 30-50 kg/m^3 if I remember right? So the difference in mass is SO big that any practical thickness of the soft stuff simply can not be effective for blocking.

LF is somewhat blocked AND also absorbed by the walls

Spot on. That would actually be the goal.

Regarding

overly focused on "soundproofing"

...

This is most often not a choice, it's dictated. And it really depends on what someones idea of a "studio" actually is. In many cases it's more like a place that has loads of recording equipment inside, sure, but what you actually mostly do is play acoustic drums 4 hours a day, 4 days of the week and your neighbours garden is 10 metres from the door. You HAVE to focus on extreme soundproofing. Suburban life.

 

[miroslav]

This is most often not a choice, it's dictated. And it really depends on what someones idea of a "studio" actually is. In many cases it's more like a place that has loads of recording equipment inside, sure, but what you actually mostly do is play acoustic drums 4 hours a day, 4 days of the week and your neighbours garden is 10 metres from the door. You HAVE to focus on extreme soundproofing. Suburban life.

Unless you build something out of poured cement, about a foot thick and detached...you're not going to get soundproofing, IMO.
Like I said, for soundproofing, it's gotta be an almost from the ground up build.
It's funny how easily sound will pass through a lot of structures and materials.

So...if the goal is for your neighbor to not hear you playing drums 4 hours a day, 4 days per week...I think you will have hard time.
I mean...would your neighbor be OK with hearing them less, but still 4 hours a day, 4 days per week...?...because sometimes even a low-level repeating noise can be just as irritating as a loud one when heard endlessly. Like the drip of a sink...or the small vibration of a ceiling fan...etc.

But anyway...since you're not concerned about audio quality or build-up of LF in the room (or are you?)...and if all you want is to practice, and you don't care what it sounds like...then try your 10 layers of whatever.
Just keep in mind that you have to attach them somehow, to something...and if that happens to be the house wall studs and/or ceiling joists, etc...that blocked sound will travel through the hard surface connections to the other rooms and/or outside.

Maybe you should move to the country.

Damn...4 hours a day, 4 days per week...you must be really good...or maybe not, and that's why you need so much practice?

I wish I had the time right now to put in a couple of hours per day...but soon I will...my studio construction is slowly coming to an end.
I've got neighbors, but not 10M away...so my construction took that in mind, and I think I should be fine with how loud things will get.
Here it's no big deal during the day...and at night, you can go up to 11PM, and no one will say anything.
I've been banging nails and running circular saws at 11-12PM...and I asked my closest neighbor if he hears any of my late night construction noise...and he said no. That's at about 40-50M away...so I think my thick insulation, heavier outer layer and double drywall inside is doing a decent job.

 

[sasquatch]

https://nationalgypsum.com/file/THESOUNDBOOK.pdf

g

 

[spitzer]

Unless you build something out of poured cement, about a foot thick and detached...you're not going to get soundproofing, IMO.
Like I said, for soundproofing, it's gotta be an almost from the ground up build.
It's funny how easily sound will pass through a lot of structures and materials.

So...if the goal is for your neighbor to not hear you playing drums 4 hours a day, 4 days per week...I think you will have hard time.
I mean...would your neighbor be OK with hearing them less, but still 4 hours a day, 4 days per week...?...because sometimes even a low-level repeating noise can be just as irritating as a loud one when heard endlessly. Like the drip of a sink...or the small vibration of a ceiling fan...etc.

But anyway...since you're not concerned about audio quality or build-up of LF in the room (or are you?)...and if all you want is to practice, and you don't care what it sounds like...then try your 10 layers of whatever.
Just keep in mind that you have to attach them somehow, to something...and if that happens to be the house wall studs and/or ceiling joists, etc...that blocked sound will travel through the hard surface connections to the other rooms and/or outside.

Maybe you should move to the country.

Damn...4 hours a day, 4 days per week...you must be really good...or maybe not, and that's why you need so much practice?

I wish I had the time right now to put in a couple of hours per day...but soon I will...my studio construction is slowly coming to an end.
I've got neighbors, but not 10M away...so my construction took that in mind, and I think I should be fine with how loud things will get.
Here it's no big deal during the day...and at night, you can go up to 11PM, and no one will say anything.
I've been banging nails and running circular saws at 11-12PM...and I asked my closest neighbor if he hears any of my late night construction noise...and he said no. That's at about 40-50M away...so I think my thick insulation, heavier outer layer and double drywall inside is doing a decent job.

Yes I am concerned about "LF build up in the room" and things like that. But like many other people (?) I can not choose to tear the place apart and do exactly what I want.

10 layers of whatever? It's already there. So you see, the question is more like, would it be worthwhile to tear half of it down ONLY TO make the construction more "standard" and "proven"? Or indeed, like I think I asked originally, why exactly would I want to have 50 mm, or 150 mm, or whatever thickness of ROCKWOOL in there?

I'd like to stick to the comparison between pure mass ("10 layers of whatever") versus the regular "two layers of drywall and rockwool" if and when it gets too complicated otherwise.

I think it's already well known that almost anything will block HF waves. So from a blocking standpoint, especially if the neighbours are relatively close, the ONLY problem that remains in that domain is Low Frequency blocking. (Think more "band playing live" instead of "recording studio" here: ) Bass drums and bass guitars go down to VERY low frequencies, below 100 Hz, even below 50 Hz. How DO you deal with that if not with mass and lots of it?

Depending on what exactly you mean by "soundproofing", it's either impossible or actually feasible in the real world. Considering solo drums in a small room are typically in the 100 dB range with peaks some measure higher... reducing that by 40 dB is not impossible. You don't need to make the sound disappear completely, just get it down or close to the ambient level outside. Then it will actually "disappear" with the wind.

re: moving to the country... I'll need to start another topic about that.

 

[spitzer]

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Some time ago, maybe within the last year or so, I found a relatively recent research paper (I think it was Canadian, but not 100% sure) but lost it since... It addressed the different types of walls with different styles of cavities AND included data about the FREQUENCY spectrum of the reduction which I hadn't seen anywhere else before. I'll post if if I can find it again, for anyone interested.

 

[jamesperrett]

There are some good papers by G.D. Plumb on the BBC Research website with the attenuation of different wall types at different frequencies which are very interesting.

Scroll down to near the bottom of the list at

G.D. Plumb - BBC R&D

 

[miroslav]

Or indeed, like I think I asked originally, why exactly would I want to have 50 mm, or 150 mm, or whatever thickness of ROCKWOOL in there?

I'm pretty sure that question was answered already...but here it is again...

The fiberglass/rockwool creates damping by its fibrous nature. Sound waves are absorbed rather than reflected.
I think that's a pretty obvious thing...that when you put fibrous broadband or LF traps in a room, they absorb/reduce the sound...so I'm not understanding why you seem to reject that and you keep asking why would you use those materials in favor of hard surface materials...?

 

[spitzer]

I'm pretty sure that question was answered already...but here it is again...

The fiberglass/rockwool creates damping by its fibrous nature. Sound waves are absorbed rather than reflected.
I think that's a pretty obvious thing...that when you put fibrous broadband or LF traps in a room, they absorb/reduce the sound...so I'm not understanding why you seem to reject that and you keep asking why would you use those materials in favor of hard surface materials...?

What are you talking about? There are no bass traps or absorbers or any kind of "room treatment" involved.

The post you quoted, did you read it at all? Seriously.

I can't think of a way to put the question more simply than which type of isolation wall would block low frequency waves better than something-or-other. The answer however is not simple.

I've read countless times that the standard 2 layers of fibreboard/drywall on the inside, some amount of rockwool in the cavity sandwiched in there with another layer of fibreboard on the other side is effective... except it does NOT effectively block the very low frequencies (less than 100 Hz) I'm talking about.

 

[spitzer]

Going back a little bit and trying to stick to the point...

I agree that "10 layers" of anything is denser than 2 layers...but with some things, there's the reality check that makes 10 layers undoable.

We must be living in a different reality... but that doesn't even matter. The question is simply about performance.

It takes a lot to stop and/or absorb very LF...so mass and density are key, and a combination of both fiberglass/rockwool and drywall/plasterboard of a few layers rather than 10 layers and no insulation, is the better solution.

That's the key. Which combination is the best, and for what purpose?

I'm sure most people will agree that for example a 50 cm thick solid concrete wall will block sound very effectively. Why would 10 layers of drywall or fibreboard be different in that respect? Mass is mass.

 

[jimmys69]

Think about why an acoustic guitar makes sound. It resonates in the open cavity. The same happens in a hollow wall. That is the purpose of insulation in the cavity. Not so much to stop transition of sound.

 

[spitzer]

Think about why an acoustic guitar makes sound. It resonates in the open cavity. The same happens in a hollow wall. That is the purpose of insulation in the cavity. Not so much to stop transition of sound.

Sure, of course. However are we (all) somehow picturing this differently? Is that the confusion? There is no cavity in the thing I tried to describe. What I meant was simply 10 layers of board all in contact just with each other. Perhaps glued or nailed together. No open cavity/ies. So 10 layers of 2 cm board in this configuration just makes one 20 cm thick massive wall. Depending on the density of the board(s) it could well be more massive than a thinner brick wall plastered on both sides. (Off the top of my head, for a reasonably sized wall/door it would easily weigh a ton, 1000 kg)

I hope I'm making sense now...?

 

[spitzer]

There are some good papers by G.D. Plumb on the BBC Research website with the attenuation of different wall types at different frequencies which are very interesting.

Scroll down to near the bottom of the list at

G.D. Plumb - BBC R&D

For me it was the first one from the top...? One about "improved low frequency attenuation ...". That paper is remarkably similar to the Canadian (?) paper I read some time ago.

And indeed very interesting. One thing in particular... the paper refers to an "all plasterboard" thing... that is almost the opposite of all plasterboard. It makes sense in the context of that paper, sure, but that's actually what I was theoretically comparing against. I would call that "double plasterboard with air gap", because "all plasterboard" in my mind is: | | | | | | | | | | | (I'm sure that graphic looks awesome )

Very very interesting in the sense that as far as I can read it correctly, the 2x board - thin air - 2x board structure (31 cm thickness) looks to have a reduction of 30 dB at the lowest measured frequency (63 Hz). I wonder now... what would be the difference between that and an actual ALL plasterboard wall of the same thickness? One difference of course is that since there are no studs, how they're placed has no meaning and since there's no fiberglass, its thickness and where it's placed also has no meaning.

This stuff is fascinating. You'd think in this day and age they'd have computer software that could simply calculate what happens when pressure waves hit different mediums with known molecular structures and densities... but I guess not?

 

[miroslav]

I hope I'm making sense now...?

No...you are lost in your own circular discussion.

*YOU* asked the question...why fiberglass/rockwool instead of the fiberboard/drywall (or whatever your 10 layers are made of)...?...and multiple times the question is answered.
Fibrous material like fiberglass and rockwool dampen vibrations and absorb sound waves by converting their energy to heat....that is how they reduce sound compared to the materials you're considering, which do not.

Yet you then come back over and over, and say no one is understanding what you are talking about.

I would think by now you could have experimented with the different materials and found out for yourself what everyone is telling you.

 

[spitzer]

No...you are lost in your own circular discussion.

*YOU* asked the question...why fiberglass/rockwool instead of the fiberboard/drywall (or whatever your 10 layers are made of)...?...and multiple times the question is answered.
Fibrous material like fiberglass and rockwool dampen vibrations and absorb sound waves by converting their energy to heat....that is how they reduce sound compared to the materials you're considering, which do not.

Yet you then come back over and over, and say no one is understanding what you are talking about.

I would think by now you could have experimented with the different materials and found out for yourself what everyone is telling you.

What...? I was replying specifically to jimmys69 who was talking about a "hollow wall".

Compared "to the materials you're considering"... again, what??? Experimenting with what different materials? What the hell are you talking about dude.

 

[miroslav]

THIS is what I'm talking about...your own first post where you asked questions...and now you're acting like you don't know why people are answering them.

Rockwool, fiberglass and similar materials only absorb or block high frequencies, so why would one use them at all as part of the construction?

.....

I would assume that 10 layers of fiberboard would block low frequencies more effectively than 2 layers of fiberboard and whatever thickness of rockwool behind it (air gap or not, your choice). Right or wrong?

Take the materials you mentioned above ^^^...and EXPERIMENT with them until YOU find what works for YOU.
You are wasting time talking about it....go try it out.

This thread is going nowhere because you keep coming back to the same questions...and then you seem confused when you get the same answers.