Question about Mineral Wool

Folkcafe

Active member
The problem with the sponge analogy is that a sponge will saturate because the water doesn't change. WIth sound absorption, the sound energy is actually converted to heat. Unless you are putting kilowatts of sound energy out, it's not going to "saturate" to the point that you can even detect the increase in temperature.

Instead think of it more in terms of light. Things will absorb specific wavelengths of light, and reflect others. Those absorbed are converted to heat. A black curtain will absorb the majority of the light. A medium grey will also absorb the same wavelengths, just at a lower efficiency. White will reflect all wavelengths back. A red curtain absorbs the light but reflects back red. Likewise, certain materials are going to absorb different sound frequencies, based on density, rigidity, and thickness. The glass that is used to make OC703 would probably make a nice reflective window if cast into a smooth, very rigid plate.

The biggest problem for most people is that measuring sound is not as easily done and interpreted as viewing a room and looking at the light. It's easy to see that the corner is darker, or seeing a light reflecting in a mirror or off a window. Hearing bass bloom in the corner is the same as getting the reflection of a lamp in a mirror.

Putting up a thin layer of low density fiberglass for sound control is about as effective as putting up sheer curtains to keep the sunlight out of your room. Putting up a wall with mass loaded vinyl and rockwool panels is like adding thick blackout curtains.

Ok, lets take your light analogy. A light absorptive material will only absorb a portion of light and reflect the rest. Simply stated a surface's ability to absorb light is finite. Does that really change the analogy though? Both analogies are off as light is both particle and wave and water is a liquid which is different from sound waves transmitted though air molecules. I chose the later for simplicity but neither is a direct correlation.

You seemed to miss the more relevant point, that with sound energy, an absorptive material will become reflective at some point which is dependent on the sounds ability to pass through it in order to be converted to heat. If it can't pass through, it is reflected. This is especially prevalent with lower frequencies, which is where most are in need of treatment.

The things we want sometimes requires a base amount of effort and learning. Can anyone do it? I am pretty well convinced the answer is no but guessing or hoping something will work won't change the laws of physics for them.

I had studied the handbook of acoustics pretty extensively more than 20 years ago. In refreshing my knowledge base recently, I got my ass handed to me many times by relying on broad rules of thumb that I had extrapolated out, only to do the math and be reminded how unintuitive acoustics is.

So lets say you want to build a bass trap 2ft thick. Here is a chart with two different fiberglass products. Which would you pick?

Screen Shot 06-24-22 at 04.54 PM.JPG
 

TalismanRich

Well-known member
Ok, lets take your light analogy. A light absorptive material will only absorb a portion of light and reflect the rest. Simply stated a surface's ability to absorb light is finite. Does that really change the analogy though? Both analogies are off as light is both particle and wave and water is a liquid which is different from sound waves transmitted though air molecules. I chose the later for simplicity but neither is a direct correlation.
I would say that light is closer a analogue in that it a wave, just at a much higher frequency. However, I will admit that there is a difference in the conversion mechanism from sound. With sound waves, the degradation in level is mostly due to vibrational friction creating heat and reflection is simply of a portion of the wave that could not be converted to heat bouncing back, similar to a mirror. With light, the reflected color actually is due to the light's energy causing a jump in electron energy level of a specific portion of the compound, and the resulting return to the previous level. Absorption is simply converted to heat.

You seemed to miss the more relevant point, that with sound energy, an absorptive material will become reflective at some point which is dependent on the sounds ability to pass through it in order to be converted to heat. If it can't pass through, it is reflected. This is especially prevalent with lower frequencies, which is where most are in need of treatment.
I completely agree that, given a particular material, having a thicker section with more ways for the sound pressure to be dissipated is the way to go. Based on the the modelling, I would expect you could calculate how to equate the two different materials to get the same amount of sound dissipation.
 
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Folkcafe

Active member
So both are Owens Corning fiberglass. The blue is 703 at 2ft thick. The green is cheap Owens Corning Pink insulation available at Home Depot also at 2ft thick. To be effective your choice should be at least .75 at the frequency you wish to treat. The pink fluffy stuff is at least .75 effective to 40hz vs only 300hz for 703.

703 used to list a .85 rating at 125hz. The updated rating is now .63 at 125hz for 4 inch thick. Think about this. Great maybe if you only have 4 inch panels. Compare how it performs in this graph at 24 inches and you see what I mean. Going thicker, doesn't gain much of anything. Now if I measured 4 inches of the pink fluffy stuff, the 703 beats it handily. At 24 inches for both, pink out performs it by a mile. What I had to do to compare these, involved looking up a few specifications and running a online calculator.

In going over my pre-construction notes, here is another comparison OC Pink with Safe N Sound RB40.

Screen Shot 06-24-22 at 07.10 PM.JPG
 
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Ed Fones

Well-known member
Would this apply to the normal house insulation as well? Meaning that normal house insulation at a certain thickness is just as efficient if not more?

Or am I misunderstanding this?
 

Folkcafe

Active member
Would this apply to the normal house insulation as well? Meaning that normal house insulation at a certain thickness is just as efficient if not more?

Or am I misunderstanding this?
Well the "pink" stuff I refer to is just normal house insulation. Depending on product, the GFR rating varies for a whole bunch of reasons. To explain it further, I'll stick with the Light analogy to make Rich happy.

So picture a window screen. Part is solid, part is open. One layer pretty much lets most of the light through but if you've ever compared a window without a screen and one with, you see there is a difference. Now imagine 10 layers of screen. Now 100 then 1000. At what point is light no longer effectively making it through. Now vary the screen grid and make some smaller and others larger. Then layer them. The larger grids at 100 layers will let a lot more light through than the smaller. In order for the insulation to absorb, sound needs to penetrate through the materials or else it is ultimately seen acoustically as a solid surface and reflects back. Some will be absorbed but with the limits you see in my graphs. All materials will hit this limit no matter what it is. So what works best at 6 or 10 or 12 or 24 inches varies.

So what are you designing? Bass trap, broadband absorber, maybe a ceiling cloud. What lower limit is acceptable to you? How would you know? Do I need some obscure material that is hard to find or can I just use basic stuff from a big box store?

Acoustic testing is done on tons of building materials. When I worked at Bose, there was a software package called Modeler. You built a virtual space and it used these ratings for everything from the concrete to seating materials. It very much had limits especially for small spaces but big venues, it worked very well.

GFR testing has been going on for some time but insulation manufacturers don't typically publish this data. I started a spreadsheet when I was planning my remodel and gathered data on all the various products I could get locally at Home Depot and Lowes. I added some from online vendors of acoustic products then compared all of them. Pink fluffy varies at between 3600 and 5000 depending on product. I got 2ft x 4ft R38 and placed them sideways along my entire back wall and in 2ftx2ft traps in the front corners. Out of everything, it was the only choice that effectively got down to 40hz at .75 without going membranes or resonators.

I see a lot of suggestions to use this or that without much data to support what you can actually expect for performance. Use whatever you want but at least know what you can expect from it. In doing the comparisons, you'll find that product X works better than product Y at 6 inches but at 10, product Y is more effective at lower frequencies than 10 inches of X. That is the whole point in the exercise. There is no this is better than that without the context of analysis in a specific application.
 

Ed Fones

Well-known member
Ok and I am not disagreeing, but I have used normal household insulation and Rockwool RW3 acoustic. The acoustic is made differently and denser. They also say that household insulation shouldnt be compacted otherwise it loses its insulating qualities. But are you saying if we get household insulation and squash it down and even add more, it will be just as good or even better than acoustic insulation?
 
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Folkcafe

Active member
Ok and I am not disagreeing, but I have used normal household insulation and Rockwool RW3 acoustic. The acoustic is made differently and denser. They also say that household insulation shouldnt be compacted otherwise it loses its insulating qualities. But are you saying if we get household insulation and squash it down and even add more, it will be just as or better than acoustic insulation?
I don't know where you get the idea that I said anything about squashing it down. I am only talking about the thickness of the various material used. You can get insulation in a variety of thicknesses and also you can stack them together to make absorbers even thicker. GFR is a material construction specification and is not dependent on thickness. It is also the rating of the insulation when fully expanded to its proper dimensional size. R30 is 9.5 inches for instance. Compressing it would change the GFR.

What I am saying is that density is not the most important aspect to absorption. How well sound penetrates and is absorbed, without being reflected, is what is important. Gas Flow Resistivity aka the ability for sound to penetrate. We are talking about sound waves traveling on air molecules. Once those sound molecules hit sufficient resistance of the insulation, it acts as a solid surface and is reflected. How thick depends on the material. For really thick bass traps, lower GFR materials like pink household insulation will out perform higher GFR and more dense insulation like rockwool. Somewhere at a thickness in between, the rockwool will outperform at less thick low GFR insulation. How do you know which and what to use for a particular application? Run the numbers and compare.

Question, how did you know Rockwool RW3 Acoustic would be effective for your sound treatment requirements? What data did you use?
 

Ed Fones

Well-known member
I don't know where you get the idea that I said anything about squashing it down. I am only talking about the thickness of the various material used. You can get insulation in a variety of thicknesses and also you can stack them together to make absorbers even thicker. GFR is a material construction specification and is not dependent on thickness. It is also the rating of the insulation when fully expanded to its proper dimensional size. R30 is 9.5 inches for instance. Compressing it would change the GFR.

What I am saying is that density is not the most important aspect to absorption. How well sound penetrates and is absorbed, without being reflected, is what is important. Gas Flow Resistivity aka the ability for sound to penetrate. We are talking about sound waves traveling on air molecules. Once those sound molecules hit sufficient resistance of the insulation, it acts as a solid surface and is reflected. How thick depends on the material. For really thick bass traps, lower GFR materials like pink household insulation will out perform higher GFR and more dense insulation like rockwool. Somewhere at a thickness in between, the rockwool will outperform at less thick low GFR insulation. How do you know which and what to use for a particular application? Run the numbers and compare.

Question, how did you know Rockwool RW3 Acoustic would be effective for your sound treatment requirements? What data did you use?
Thats a simple one. I came here and read the posts on which acoustic insulation to use available in my country. :unsure:

I have since found out that companies that deal in acoustic treatments use a variety of other materials and methods to treat room acoustics. Even foam which is scorned on here.

I have also tried to work out that sound only travels in air. So it has to travel into the through/among the material freely. If it is restricted by a membrane like plastic, then that will act as a barrier and reflection. Polystyrene is another useless product because air cannot travel through it, although used as a thermal insulation. My point being heat and sound 'can' behave differently with different insulations.

I know that RW3 is made different than fluffy stuff, so I assumed that was the answer, but must admit expected more of a eye opening difference between the two when being used. I was disappointed.
 
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Slouching Raymond

Active member
I have also tried to work out that sound only travels in air.
Sound travels in everything. It travels well in water, as any whale will tell you. It is discontinuities that cause reflections. i.e. a change in the densities of materials.
So, if you had a stack of tiles made from steel, wood, plastic, lino etc, you will get multiple reflections, one from each boundary.
 

rob aylestone

Well-known member
The trouble with specs is that at best, they give you what should happen, so you make a choice. Has anyone built a studio, and then replaced whatever they used with something else? We do exactly the same with the wall and ceiling cladding. My first had two layers of plasterboard on the internal room within a room stud work. Flight cases, guitar amps and drums soon dug holes in the plasterboard. The next studio had a layer of plasterboard, then a layer of lightweight insulation board, then plasterboard finished with MDF. The MDF when painted looks like plaster, but is much tougher when hit with anything. It's also denser and this room was great with drum kits - nothing escaped. Did that layer of insulation board actually do anything? I have no idea. This was freestanding, so you could actually walk around the gap between it and the outside world brickwork and concrete. I finished it off with a single skin of plasterboard, with nothing in the cavity at all. With nothing getting through, would stuffing that gap with something have done anything? Again, I don't know. Next one did NOT have the insulation board and seemed to be just as good. However, the ceiling was not so good. two layers of plasterboard was not enough Dropping Rockwool into the gaps between the timber, and then laying 18mm MDF on top, with a few dogs of adhesive was as much as I could access. This MDF (and??) the Rockwool worked. I've been lucky? I don't know if any of these would have been compromised by adding or subtracting a layer? I do wonder if some of my studios wasted money with just one additional layer, when the leak was the door!

One of my studios was compromised by the floor - the walls and ceilings were fine (and normal) but the room downstairs where occasionally people played bass or drums in for practice came through the floor and downstairs ceiling - we did mostly cure it by a two layer MDF floor with a thin layer of sponge sheet between them, but clearly much of the studio wall was a bit pointless?
 

Folkcafe

Active member
Thats a simple one. I came here and read the posts on which acoustic insulation to use available in my country. :unsure:

I have since found out that companies that deal in acoustic treatments use a variety of other materials and methods to treat room acoustics. Even foam which is scorned on here.

I know that RW3 is made different than fluffy stuff, so I assumed that was the answer, but must admit expected more of a eye opening difference between the two when being used. I was disappointed.
And companies that deal with acoustic treatments use a bit of science and engineering. Reputable commercial acoustic treatment manufacturers do something called lab testing of their products and publish the data so that the buyer has an opportunity to evaluate the efficacy for their acoustic issues. All these materials have a range of effective frequencies, yes, even foam. The question becomes, how wide a range of frequencies do you need to solve your fundamental problems?

Seems to me anyone who builds a studio space is recording and mixing audio. It seems rather obvious that one should have a basic idea of audio spectrum in applying EQ and mixing various sources. I'm trying to gently ease into this question. How did you determine what frequencies you need to treat for in your studio space? How did you evaluate these two products, at the thickness you used, as to how they would perform?

You say you were disappointed. What were you expecting, magic? I know I'm walking a line where I could come off as being overly harsh. Sometimes the most obvious problem like flutter is masking other issues. Many who have been through this know the rabbit hole it can become. Yes, for some it can be a little overwhelming.

This is homerecording.com where gathered are those who desire to be musician, songwriter, producer, engineer and for many, at least rudimentary studio builders. If someone told you that if you want to be a songwriter, that it requires effort to learn the craft, most would have no issue with the advice. Is it not the same for those who wish to acoustically treat their studios? If I say you probably want some basic understanding of the problem is that too heavy an ask? DIY can yield great results but that is totally dependent on knowledge, otherwise you are depending on just dumb luck.
 

rob aylestone

Well-known member
I think most of it is dumb luck. I've been reading about it since around 1980. I've taken all the successes on board and in the main, avoided the things that caused others problems. In addition, I've looked for ways to remove problems caused by construction too hard for me to do properly. I have a list of always do, try to do and avoid. Sometimes you are forced to cut a corner, and over the years I'm better at assessing how damaging it will be!
 

Folkcafe

Active member
I think most of it is dumb luck. I've been reading about it since around 1980. I've taken all the successes on board and in the main, avoided the things that caused others problems. In addition, I've looked for ways to remove problems caused by construction too hard for me to do properly. I have a list of always do, try to do and avoid. Sometimes you are forced to cut a corner, and over the years I'm better at assessing how damaging it will be!
Apples and oranges? My discussion is only focused on acoustic treatment, not construction which really for most, is another topic. Many here are trying to utilize an existing space for recording. Is it still all really just dumb luck?

I posted my room model which I confirmed via room measurement. Had fundamental modes at 20-40-80-160hz which measurement confirmed. As most of my work doesn't go into the 20's I engineered my room treatment to be .75 effective to 40hz. How? I gathered the data on all the products I could purchase locally or online. This part was probably the most time consuming, other than actual construction of the treatment. I then began comparing each at different depths using an online calculator. That part was actually the easiest part of the process. In this case the R38 batts at 2ft thick outperformed everything else as the graphs I posted show. For bass traps, nothing else came even close. I guess I was just lucky.
 

Ed Fones

Well-known member
And companies that deal with acoustic treatments use a bit of science and engineering. Reputable commercial acoustic treatment manufacturers do something called lab testing of their products and publish the data so that the buyer has an opportunity to evaluate the efficacy for their acoustic issues. All these materials have a range of effective frequencies, yes, even foam. The question becomes, how wide a range of frequencies do you need to solve your fundamental problems?

Seems to me anyone who builds a studio space is recording and mixing audio. It seems rather obvious that one should have a basic idea of audio spectrum in applying EQ and mixing various sources. I'm trying to gently ease into this question. How did you determine what frequencies you need to treat for in your studio space? How did you evaluate these two products, at the thickness you used, as to how they would perform?

You say you were disappointed. What were you expecting, magic? I know I'm walking a line where I could come off as being overly harsh. Sometimes the most obvious problem like flutter is masking other issues. Many who have been through this know the rabbit hole it can become. Yes, for some it can be a little overwhelming.

This is homerecording.com where gathered are those who desire to be musician, songwriter, producer, engineer and for many, at least rudimentary studio builders. If someone told you that if you want to be a songwriter, that it requires effort to learn the craft, most would have no issue with the advice. Is it not the same for those who wish to acoustically treat their studios? If I say you probably want some basic understanding of the problem is that too heavy an ask? DIY can yield great results but that is totally dependent on knowledge, otherwise you are depending on just dumb luck.
You are hitting all the nails on the head with 100% accuracy. I could build the studio but for the insides I came here for info.

Yes I expected magic from RW3. I lined the inside of the sound booth with acoustic foam tiles. I think 250 of them. Then I inserted bass traps in each corner then later I hung 4x2ft RW3 panels over the foam tiles. It works for us. It produces a nice flat sound booth to record vocals.

The other room I assumed that just hanging RW3 panels on the wall and ceiling would do the job for video. A much bigger room. It did nothing and Rob's suggestion of duvets all around as well actually did the job.

Conclusion...........RW3 does work, but only if it is around the room 100% or used with something else making the coverage 100%. Hanging pretty panels every now and again does f*ck all but waste time and money no matter where you position them. The sound has to be captured to reduce reverb. Anything it can bounce off it will.

I am sure you will agree?
 
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Folkcafe

Active member
The proof is in the pudding


Are we talking sound proofing or sound treatment? People often use these terms interchangeably, but they are not the same. Answer and maybe I'll take time to watch but I do know about both.
 

Folkcafe

Active member
You are hitting all the nails on the head with 100% accuracy. I am a carpenter who throws a hammer at nails and sometimes gets lucky. I could build the studio but for the insides I came here for info.

Yes I expected magic from RW3. I lined the inside of the sound booth with acoustic foam tiles. I think 250 of them. Then I inserted bass traps in each corner then later I hung 4x2ft RW3 panels over the foam tiles. It works for us. It produces a nice flat sound booth to record vocals.

The other room I assumed that just hanging RW3 panels on the wall and ceiling would do the job for video. A much bigger room. It did nothing and Rob's suggestion of duvets all around as well actually did the job.

Conclusion...........RW3 does work, but only if it is around the room 100% or used with something else making the coverage 100%. Hanging pretty panels every now and again does f*ck all but waste time and money no matter where you position them. The sound has to be captured to reduce reverb. Anything it can bounce off it will.

I am sure you will agree?
Sure...if that's what you want? Many studios have live rooms. Not exactly dead. An example would be a big room for piano or cello. Even acoustic guitar in a great sounding room, man is there anything better in life? Sadly, most of us, including myself don't have such a space. I did classical recording professionally. There it is all about the room.
 

Ed Fones

Well-known member
Sure...if that's what you want? Many studios have live rooms. Not exactly dead. An example would be a big room for piano or cello. Even acoustic guitar in a great sounding room, man is there anything better in life? Sadly, most of us, including myself don't have such a space. I did classical recording professionally. There it is all about the room.
:unsure:

When the room causes problems with the mic sound, then I have no choice and that was with 3 different mics.
 
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