Acoustic treatment books

[CristianoLO]

Do you have a reference library on acoustic treatment and panel building? I saw this book, I haven't bought it yet because for me it would be an import (taxes, long waiting...) and I don't know if it's something really worthwhile, if it shows how to calculate, explains the usability of each type of treatment, or if it's something that is just about woodworking.

Aviso de redirecionamento

 

[Danaxus]

I don't know of any books dedicated to treatment alone, though there are a few which cover the science of acoustics and psychoacoustics. If you're looking for guidance on treatment alone, the best resource I found was acousticsinsider.com. This is a paid-for service, that gives you access to written guides and videos explaining what type of treatment exists, which ones to use, why the particular treatment is best for a certain situation, the reasoning behind it, and how to DIY build them yourself (complete with material lists and carpentry guides).

Some caveats now: the acoustician behind the site, Jesco Lohan, heavily favours porous absorption, almost to the exclusion of anything else (at least in the room sizes you'd typically find in a house). He has plenty of experience building these and seems to understand the science very well. He also provides plenty of real-world examples of treatments he's helped build/design, along with REW measurements and photos of the space. That said, there are plenty of people both here in the forums and on other acoustic sites (like gearspace), who vehemently disagree with his methodology (@Bjorn comes to mind).

Another caveat is that Jesco specifically targets his treatment plans at professional audio technicians, and clearly states it's not for audiophiles. I have yet to hear an explanation of how these two groups are supposed to differ in terms of music listening - presumably the technician mastered the music in a way that maximises their enjoyment of it, and so treating your listening room the same way they treated their studio, should most faithfully recreate what they perceived to be as close to the perfect way to experience that music, no? I think I heard something about technicians wanting to hear every last detail of a song, more than enjoy it - but isn't hearing details enjoyable?

The main argument I hear against the porous absorption method proposed by Jesco, is that it will deaden the room, and isn't good at managing frequencies below 100Hz. For what little it's worth, I haven't found those arguments compelling. Firstly, what exactly is a "dead" room quantitatively? Does it mean uneven timing? Uneven reverb? Does it mean too little reverb, regardless of the how even it is across the frequency spectrum? How much is too little - below 500ms? How do we know this, are the studies? Polls? Is this from personal experience building rooms? Hearsay?
Regarding the low frequency effectiveness, Jesco says with a reasonable amount of it, you can get control down to 40Hz. As aforementioned, he shows before/after REW measurements to prove it. The only counter arguments I've heard are "no it doesn't - trust me".


Bottom-line, the people arguing that there are better ways to treat rooms other than brute-forcing it with porous absorption, may very well be right. However, they all essentially ask you take their word for it and at that point how do you differentiate between them and a snake-oil salesman? I'm not saying they are - there are clearly very experience professionals here and elsewhere online. All I'm saying is that, unless they take the time to explain themselves, how on Earth is a non-professional supposed to tell them apart? But on the other hand, why should they take time out of their day to write up explanations for free?

 

[ozzy9832001]

Another caveat is that Jesco specifically targets his treatment plans at professional audio technicians, and clearly states it's not for audiophiles. I have yet to hear an explanation of how these two groups are supposed to differ in terms of music listening - presumably the technician mastered the music in a way that maximises their enjoyment of it, and so treating your listening room the same way they treated their studio, should most faithfully recreate what they perceived to be as close to the perfect way to experience that music, no? I think I heard something about technicians wanting to hear every last detail of a song, more than enjoy it - but isn't hearing details enjoyable?

The main argument I hear against the porous absorption method proposed by Jesco, is that it will deaden the room, and isn't good at managing frequencies below 100Hz. For what little it's worth, I haven't found those arguments compelling. Firstly, what exactly is a "dead" room quantitatively? Does it mean uneven timing? Uneven reverb? Does it mean too little reverb, regardless of the how even it is across the frequency spectrum? How much is too little - below 500ms? How do we know this, are the studies? Polls? Is this from personal experience building rooms? Hearsay?
Regarding the low frequency effectiveness, Jesco says with a reasonable amount of it, you can get control down to 40Hz. As aforementioned, he shows before/after REW measurements to prove it. The only counter arguments I've heard are "no it doesn't - trust me".

A dead room is a room that has very fast decay times. Well under 200ms and virtually no reflections. The room is so well treated that it is actually a bit unnerving to be in. Not quite to the levels of an anechoic chamber, but you get my point.

The reasoning behind it stems from how we hear. We need reflections and their subsequent effects to help us locate where a sound is coming from. It also helps with our sense of space and balance. For most audiophiles a decay time of 300ms at 60hz is considered acceptable. At 200ms, a 60hz kick drum has a fairly natural, quick decay. Take a kick drum outside and smack it. Sounds nice and tight. Can really hear the transient. Bring it inside, do the same thing. Hear and echo as it blasts around the room. Do that several times and you'll see how quickly it gets muddy.

Why this is important is it prevents the kick or bass guitar (if tuned that low) from drowning everything out. You know you have a good room setup when you can start to hear the different bass notes in addition to the drum. Often times, you can't. This is especially true with classical music or even a lot of metal genres.

For me, I only need to go to about 60hz. Most of the music I listen to the kick is actually closer to 80hz then 60. Classical has a lot of organ music which can go into the 30s. A bass can go down to 40hz, but rarely does.

Most 100% porous absorption is velocity based. So, the sound has to hit it in order for the sound to be transferred to be absorbed (converted to heat). Velocity at at wall is 0. That's why they have to be out into the room. The lower the note, the longer the wave, the more material is required to make a dent in the sound. Most bass traps are made of a combination of different material, some porous, some membrane. You can add limiters and scatter plates and other things to the traps to make them less effective at absorbing higher frequencies.

A 60hz soundwave is rough 17'. Even a 2' bass trap is nothing compared to the overall size of it.

 

[Curvature]

Acoustic Absorbers and Diffusers: Theory, Design and Application, Third Edition. Trevor Cox, Peter D’Antonio. 2016.

 

[Danaxus]

A dead room is a room that has very fast decay times. Well under 200ms and virtually no reflections. The room is so well treated that it is actually a bit unnerving to be in. Not quite to the levels of an anechoic chamber, but you get my point.

The reasoning behind it stems from how we hear. We need reflections and their subsequent effects to help us locate where a sound is coming from. It also helps with our sense of space and balance. For most audiophiles a decay time of 300ms at 60hz is considered acceptable. At 200ms, a 60hz kick drum has a fairly natural, quick decay. Take a kick drum outside and smack it. Sounds nice and tight. Can really hear the transient. Bring it inside, do the same thing. Hear and echo as it blasts around the room. Do that several times and you'll see how quickly it gets muddy.

Why this is important is it prevents the kick or bass guitar (if tuned that low) from drowning everything out. You know you have a good room setup when you can start to hear the different bass notes in addition to the drum. Often times, you can't. This is especially true with classical music or even a lot of metal genres.

For me, I only need to go to about 60hz. Most of the music I listen to the kick is actually closer to 80hz then 60. Classical has a lot of organ music which can go into the 30s. A bass can go down to 40hz, but rarely does.

Most 100% porous absorption is velocity based. So, the sound has to hit it in order for the sound to be transferred to be absorbed (converted to heat). Velocity at at wall is 0. That's why they have to be out into the room. The lower the note, the longer the wave, the more material is required to make a dent in the sound. Most bass traps are made of a combination of different material, some porous, some membrane. You can add limiters and scatter plates and other things to the traps to make them less effective at absorbing higher frequencies.

Cheers for the explanation. From what I've seen, it's really, really difficult to get decay times under 200ms. You'd need an insane amount of porous absorption, at least based on the studio designs and measurements I've seen. And controlling down to 60Hz should be quite feasible with porous if you're willing to go 15-20cm absorption plus 15-20cm air gap, at least according to what I've been researching. It's the logic I'm currently using to design my father's music room: https://www.audiosciencereview.com/...atment-plan-the-retirement-gift-update.47375/

 

[SSS]

Good site is acousticfields.com with Dennis Foley who has a lot of videos on room treatment. Also he offers panel build plans for low cost. Ethan Winer could be mentioned on bass traps. But to do room treatment DIY without measurment tools is hard to do. And all depends what one wants to achieve? An acoustically dead room without reflections or just removing low frequency room modes, and so on. An anechoic room I can say is not natural where you don't feel well. But the loudspeaker plays just it was designed with measurements in such a room. Also the off axis dispersion does not count anymore if listening on axis. Therefore there are different treatments according to a recording studio, a mixing and mastering room, home recording, home listening. For damping low frequency modes helmholz frequency adjusted resonators (bass traps) are effective, but they may be big in size to get the needed air volume. Also the type of music for listening is to know. If bass notes are not sustained then the room resonance has fewer effect than sustained notes like from an church organ.

 

[ozzy9832001]

Good site is acousticfields.com with Dennis Foley who has a lot of videos on room treatment. Also he offers panel build plans for low cost. Ethan Winer could be mentioned on bass traps. But to do room treatment DIY without measurment tools is hard to do. And all depends what one wants to achieve? An acoustically dead room without reflections or just removing low frequency room modes, and so on. An anechoic room I can say is not natural where you don't feel well. But the loudspeaker plays just it was designed with measurements in such a room. Also the off axis dispersion does not count anymore if listening on axis. Therefore there are different treatments according to a recording studio, a mixing and mastering room, home recording, home listening. For damping low frequency modes helmholz frequency adjusted resonators (bass traps) are effective, but they may be big in size to get the needed air volume. Also the type of music for listening is to know. If bass notes are not sustained then the room resonance has fewer effect than sustained notes like from an church organ.

I agree with everything you said except the part about acousticfields. While what he is selling maybe a decent product, there is little to no actual evidence to suggest it.

He is also vehemently against porous based absorption.

I have yet to meet or talk with a single individual who has had any services done by him. There are several threads already about his business, so I won't rehash them here.

However, he claims to be about the science, yet most of his videos not only contradict it, but his own previous videos.

The broad strokes are sometimes correct, but their applications are not. The comments for his videos are typically fairly neutral or negative and he never offers any real advise or solutions.

A better choice is to contact a company like GIK who has a large presence including internationally and speak with one of their associates. They are more than willing to help even if you choose not to buy anything from them. They have a number of products that will help to target specific frequency ranges and most of all, all the data is there for their products.

 

[Bjorn]

While it's possible to look at different measurements and get a decent impression, that's not necessarily a certain way of knowing it's too dead or not. It also depends on the speakers and which direction the energy in the room is arriving from. RTx measurements are useless since a diffuse field doesn't exist in small rooms.

A typical very dead space either has a very unlinear treatment like a lot of high frequency absorption and little treatment for lower midrange and bass or simply too much absorption covering surfaces. Unlinear treatment is really the worse. If the the treatment works fairly linear to subfrequencies it doesn't sound dead in the same way, even though much energy has been removed. But it will sound very dry with little energy if too much surface area has been covered.

Surgical treatment at correct places and suffieciently broadband treatment is important for a great result. I do not believe poeple generally prefer a very dry room over one that remains much energy combined with removal of audible specular energy. However, if specular energy isn't sufficiently attenuated I can understand why some think they prefer a dead room. But that's simply because the treatment hasn't been effective enough.

I believe maintaing energy and also spaciousness is crucial psycoacoustically and is very often overlooked. It's one of the reasons why treatment (the wrong type) has caused a bad impression on some. Of course if a room is super small, the room will end up sounding more dry and less spacious when removing audible room artifacts.

 

[SSS]

Good site is acousticfields.com with Dennis Foley who has a lot of videos on room treatment. Also he offers panel build plans for low cost. Ethan Winer could be mentioned on bass traps. But to do room treatment DIY without measurment tools is hard to do. And all depends what one wants to achieve? An acoustically dead room without reflections or just removing low frequency room modes, and so on. An anechoic room I can say is not natural where you don't feel well. But the loudspeaker plays just it was designed with measurements in such a room. Also the off axis dispersion does not count anymore if listening on axis. Therefore there are different treatments according to a recording studio, a mixing and mastering room, home recording, home listening. For damping low frequency modes helmholz frequency adjusted resonators (bass traps) are effective, but they may be big in size to get the needed air volume. Also the type of music for listening is to know. If bass notes are not sustained then the room resonance has fewer effect than sustained notes like from an church organ.

I mentioned Dennis Foley because of his basic videos which may help beginners in room treatment, not for professionals who have anyway practical experience.
Whether the opinion of Dennis Foley is different to other pros, this can be. Same with the mentioned Acoustic Insider, seems also to have a different view.
Anyway, DIY room treatment can be successful, to my opinion without much acoustical knowledge it will go wrong. Of course the planning and doing by a professional company is not cheap.

 

[CristianoLO]

Here above was asked about taking measurements.

Well, I already do measurements to make loudspeakers, so having a book that explains what kind of measurements should be done and the techniques involved wouldn't be a problem for me.

My intention with the topic was precisely to reach bibliographies (books, articles, websites) that indicate what and how each stage of an acoustic treatment should be done: measurements, understanding of the problems of the room, critical thinking about the limitations that it has (as in non-dedicated rooms, impediments of the wife and others), the mathematics of each type of treatment, how much I can improve for the amount of treatment I can put in, etc.

In the same way that there is already literature that can lead a DIYer to make his own anechoic measurements in a non-anechoic environment using REW and VituixCAD, is there a bibliography capable of leading a DIYer to efficient acoustic treatment solutions without going through the step of putting panels indiscriminately?

 

[Curvature]

Here above was asked about taking measurements.

Well, I already do measurements to make loudspeakers, so having a book that explains what kind of measurements should be done and the techniques involved wouldn't be a problem for me.

My intention with the topic was precisely to reach bibliographies (books, articles, websites) that indicate what and how each stage of an acoustic treatment should be done: measurements, understanding of the problems of the room, critical thinking about the limitations that it has (as in non-dedicated rooms, impediments of the wife and others), the mathematics of each type of treatment, how much I can improve for the amount of treatment I can put in, etc.

In the same way that there is already literature that can lead a DIYer to make his own anechoic measurements in a non-anechoic environment using REW and VituixCAD, is there a bibliography capable of leading a DIYer to efficient acoustic treatment solutions without going through the step of putting panels indiscriminately?

• Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms, Third Edition. Floyd E. Toole. 2017.
• Master Handbook of Acoustics, Seventh Edition. Ken C. Pohlmann, F. Alton Everest. 2021.
• Acoustic Absorbers and Diffusers: Theory, Design and Application, Third Edition. Trevor Cox, Peter D’Antonio. 2016.

These three books. The suggestions will be contradictory, however, so learning the details and whys will be necessary if you want to make informed choices. The optimal path, however, has not yet been defined.