~ Or: Why a mattress topper will STILL NOT fend off the sound of airplanes, dump trucks, or leaf blowers
If there was any degree of triggering by the small list of œffending noisemakers in that line above, then you might be a recording artist of some kind. This isn’t exclusive to voice actors, either. Session musicians, vocalists, foley creators, anyone attempting to lay a child to rest during nap time. We have all been in a position where loud external noises have interrupted one thing or another where silence was preferred and needed.
If you’ve ever been in this position, you’ve probably looked up the prospect of sound proofing to see what can be done to alleviate these concerns. Seems simple enough, right? At least based on things published on the internet. Buy some sound-proofing foam, put it up on all the walls, anecdotal allegations of effectuality, Bob’s your uncle.
Except …. it’s not that simple.
Not even a little bit.
But what’s the big deal? The internet says that sound proofing is easy! Foam, George! FOAM!
Ok.
Here’s the thing. I’m gonna go into E X C R U C I A T I N G detail about this in the coming paragraphs. You are welcome to stop here if you like. The nerd level is STRONG in this one. Because there’s a figurative æfforestation of incorrect information on the intertron, I’m diving deep.
MOST of this is going to be as it relates to room treatment. Why? Because actual sound proofing is very, very complicated. Which I will explain. As the post continues. Because WORD USAGE.
Brief aside
For any of ya’ll who have been with me for a while, you already know that I’ve written about this subject previously. As recently as November of 2022. Why am I coming back to this? Because I tried to limit the word count of the previous entry for the sake of brevity. This time, I’m going into MUCH GREATER DETAIL than before with an unhinged word count because hopefully this will be useful to somebody somewhere who really wants this level of detail. My network of connections seems to be growing as well and the question comes up more and more.
Also, it’s just one of my favorite subjects to pontificate about. So there we have it. Onward!
What Exactly is Sound Treatment?
For the sake of simplicity today, I’m going to condense the idea of sound treatment into one category: Absorption.
Insulation.
Stuffing.
I’m NOT going to get into diffusion in this post. Partly because I can already tell it’s going to be too many words for my own good. Which means more than anybody else’s good on top of it. And partly because it’s probably not helpful in a practical sense to just about any demographic who might be reading this post. Unless I’m completely off my rocker*, most of the folks reading this are going to be thinking about spaces that are relatively small. Vocal booths. Small recording rooms. Chambers that are under a size threshold where diffusion might be useful. To be fair, a small room COULD potentially benefit from s0me diffusion but it involves physics and geometry and I’m pretty sure I just had an allergic reaction thinking about it.
I MAY come back to a diffusion topic at a later date. But for today, we’re skipping it. I KNOW I just said above that I’m going to dive deeper into the subject but it’s just not specifically relevant to folks that I know who might see this.
* of course I’m off my rocker. obvi. that’s a given. but context is important.
Insulation and stuffing
The focus of this post is going to be as it relates to treatment via absorption. It’s probably the most easily accessible format by anyone who would likely read this and earth dollar for earth dollar the most beneficial. And the best part is that there is a CHANCE that someone SOMEWHERE might read this and decide -against- exclusive use of expensive and borderline-useless “foam”.
Some common and popular insulation materials used in sound absorption are Rockwool (typically Safe n Sound) and Owens Corning 700 series insulation. Not to dig on Auralex who have built an empire on “sound foam,” but you will find that it is extremely easy to build your own panels using insulation and get much more effective functionality for fewer earth dollars.
Practical DIY example
This video by voice actor June Yoon is a quick ‘n dirty method of building an acoustic panel. Is it pretty? He says it’s not but I’ve seen less pretty. Is it functional? You better believe it. Is it more cost and application effective than designer “acoustic foam?” OH YES. YES IT IS.
Side note on this: I strongly recommend use of fabrics that are acoustically transparent. Meaning that if you blow air through one side you feel all of that air on the other side. You don’t want anything to impede the effectiveness of the insulation. Burlap works great. If you want to go designer, Guilford of Maine fabrics are perfect and also fire-code compliant.
Documented effectiveness of insulation
One of the reasons I’m VERY big on the idea of using those insulation products is that there have been enough acoustic lab tests done that their absorption coefficients have been VERY THOROUGHLY DOCUMENTED. I generally won’t touch an absorption product until I can see verifiable lab testing that proves that it’s worth it.
It’s not that I’m not a risk taker or am unwilling to try new products. In fact last year Studiobricks made an announcement about an eco-friendly sound absorption panel line that sure sounds promising. No pun intended. They probably have data to review on it as well. When sound absorption is the name of the game, I want to go with something that I know is proven to work. It’s all going to cost money initially. May as well go with the thing that is going to be the most effective in terms of both function and finance.
So many reflective surfaces, so little time
Pretend like you’re looking at a new house or apartment to move into. You go into a bedroom. Four walls, nothing in it. If you clap your hands, it sounds HOT. Reverberating goodness.
All of that reverberation is coming from all of the surfaces that are not treated for sound absorption in any way.
The solution? Putting insulation panels in place that will absorb the sound. The end.
Or IS IT??
I’m going to dive a bit deeper into this because it needs to be said and you may or may not need to read it but I still need to say it!
Walls
Yup. Walls. If you’re in a square room with parallel walls, you absolutely need as much treatment as you can muster. Parallel walls will bounce sound back and forth if nothing it done to mitigate those waves. Granted they will dissipate eventually, but not before being baked into the recording or mixing process. So. Get panels on or near all the walls. That is a huge chunk of problem solved.
Bass buildup and corners
No, not the kind where you concoct an Eiffel Tower out of bass guitars. Every corner of a room is an opportunity for lower frequency waves to build up. If you’ve heard of the idea of corner traps or bass traps, those are extra thick – frequently triangular shaped – panels that will do a better job of absorbing sound that builds up in corners as the walls get closer to each other. Sometimes these corner traps are referred to as Super Chunks. Which sounds like it should be the name of a mint chocolate chip ice cream. Missed opportunity. I feel like there should be a cape involved but we’ve all seen The Incredibles. NO CAPES!
Except, hold up. I said the corners. I didn’t specify where they are. Raise of hands: when I said corners, who immediately thought of only the vertical corners?
Because guess what else is a corner? The floor to the wall. The wall to the ceiling. Those are ALSO corners where frequencies can build up. Take that into consideration when trying to solve wave problems in your space.
Do you NEED to fill every single corner of your small space with stuffing? Potentially not. Getting an evaluation of the sound of your room is a good way to figure out if anything is needed. In my own booth, there was a frequency buildup that was driving me bonkers even though I thought my treatment was solid. It was. But it’s still a small box and there are resonant frequencies involved. An extra-thick ceiling panel in one corner solved a huge part of it.
The missing surface
“But George,” you besnivel, “I covered all my walls with absorption panels and it STILL sounds like something is reflecting off of SOMEWHERE. Where could it be coming from???”
To which I will almost always reply: look up.
What’s that thing above you? The ceiling.
What makes that ceiling different from all of the other freshly treated surfaces in your room? It’s a flat surface without any treatment. Guess what’s gonna happen! Microphones are agnostic. They’ll pick up anything from anywhere and if your ceiling isn’t set, sound will go up – because it’s not exclusively directional – and bounce right off it and come back down. Into your mic.
So. Things wot need treatment? Walls, corners, and ceiling. All of the above. And to the sides. Potentially below you if it’s hard wood floor.
Who Needs Sound Treatment?
In the context of this post, sound treatment is something that you will do to a room to make it sound more …. pleasant. Maybe “dead” is the word that some folks use. For me, the word means to remove the sound of the room for the sake of capturing the tone of the thing you are trying to record.
This is the part that is mostly for my recording artist friends. Voiceover, instruments, even audio mixing. This is the domain we live in if we’re running in-home studio environments. We want the environment that we are in to be completely neutral. Why is that? A variety of reasons specific to the task at hand but they all lead to mostly the same end result. Here are some examples.
Voice Actors
As voice actors, we are told this time and again. The space that we are in needs to be completely devoid of the space that we are in. As much as possible, the sound of the room needs to be not there. The reason for this is because the mixing engineer on the other end of the recording is going to drop it into a production of some kind. If the recording you send has all kinds of room reflections in it with your voice bouncing off the walls, there’s not much they can do with it. That’s part of what is referred to as “Broadcast quality” in our requirements. When you listen to someone on the radio who is broadcasting, you don’t hear sound bouncing off the walls like when taking a shower. It’s dead as a can of spam.
It’s a bit like bending time and space, isn’t it? You’re in a room but it can’t sound like the room you’re in. But it’s the room that you need to be in to accomplish the goal of voice recording. So perfect sound treatment – and any accompanying filtration as needed – are vital to this line of work. Especially as more productions happen outside the recording facility and inside the walk-in closet.
Honorable mention: singers need most of the same stuff also. As such, please see above for anything as it relates to voice acting but apply it to singing. It’s all modular, man.
Podcasters
Is this really a requirement for podcasters? Not really. There are enough successful pocasters out there who sound like they’re recording directly from the toilet of their local rest facility that this might not be a real thing. I’m making a mountain out of a molehill.
For me? I’m a stickler. Podcasts with poor audio quality are difficult for me to listen to. Partially because I tend to listen to most of my podcasts in the car. Road noise makes it difficult as it is. And partly out of principle. It’s relatively easy to make a room sound better than barren and there are vastly superior mics with lower price points than the SM7B for that purpose. No matter what is popular.
So 50/50 on that one. It matters to me but so does uncompressed audio and look where that got me.
Speaking of dead arguments: .OGG is still the better audio format. Fight me.
Mixing Engineers
And no, I’m not referring to people who fix free-standing Kitchen Aid units. Although I’m pretty sure there’s a missed opportunity for marketing there. “First Aid for Kitchen Aid.” You’re welcome.
No, I mean mixing engineers who are involved in the mystical voodoo arts of audio kwakkery. This might be a bit niche but hear me out for a moment. Imagine, if you will, that your responsibility is to make certain that something someone else is going to listen to sounds right. No weird muddy frequencies building up that make it sound awful in your car. Or ear buds. Or that audiophile speakers system with those weird rocks on top that are alleged to make sound “purer.” I kid you not, that’s a thing that exists that does not work as advertised. I don’t even want to link to it because that might ALMOST be considered an even tacit endorsement of something that is just .. hilariously wrong on so many levels.
Where was I? Oh yeah, audio mixing.
The room that an audio engineer is working in needs to be moderately free of things that would influence the sound in a way that does not actually exist. For example, if sound is bouncing all over the walls and creating a buildup in the, say, 250hz range, the first thing that one would want to do is compensate for that. We rely on our ears for a LOT where mixing is concerned. If it sounds like 250 is building up, we’re going to filter that stuff out like a bad smell. Except the room is lying to us and there’s nothing wrong there.
The aftermath effect? The mix sounds empty everywhere else because a compensation was made for a poorly treated environment. Mixing engineers need good rooms to mix in so that what they send out to the world sounds great on everything. Ear buds, monitors, laptop speakers, cars. That’s an awful lot to try and balance for and that’s another topic for another day.
Acoustic Instrument Recordists
Yup. Outside of voiceover, you know what else sounds awful in a bathroom? An acoustic guitar. Or a hammered dulcimer. Sitar. Mandolin. Melodica. Accordion.
The process of recording acoustic instruments has a very important component of high quality room sound. For the same reason as voiceover, the room has to be well treated to avoid adding anything to the instrument recording that needs to be recorded. When you’re recording that cow bell, you want cow bell, the whole cow bell, and nothing but the cow bell. Do that cow bell justice by giving it a space to sound as deliciously good as it does on its own without any interference from the space itself.
One Last Thought on Acoustic Absorption Panels
If it’s something that you have the space for and you’re building up some acoustic panels, try as best as you can to keep them a couple inches away from the wall. Why on earth would you want to do that? Easy. If a panel is placed against the wall, a soundwave will enter the absorptive properties of the panel and bounce off the surface it’s resting against and return to the room. Filtered, yes! No question about it.
Go with me on this. It’s weird but trust me it’ll make sense.
If you put that same panel a couple inches away from the wall when sound passes through it, the absorption panel will do its filtration process. The newly filtered sound wave will bounce off the wall behind it and then BACK THROUGH the panel to be filtered even further. TWICE the absorption and filtration all by just moving the thing away from the wall a bit. CRAZY, ISN’T IT??
If you really REALLY want to dive deep into this stuff the way I have, I encourage you to review this document here. It is CHOCK full of information that is worth checking out and shows a diagram of what I am referring to above. Panels away from the walls will DO MORE than if they are against them. Sometimes that’s not possible and they must go against the walls. That’s ok too! It’s still better than nothing at all.
Sound proofing
I say those two words with trepidation. Mostly because everything PRIOR to this section is very often misconstrued as being sound proofing. There is nothing about any of the above that actually causes a space to be removed from the noises of the outside world. They will all help the internal space sound much better! But as far as external environmental audio concerns, they are not the solution.
THERE. IS. NO. SUCH. THING. AS. SOUND. PROOFING. FOAM.
<deep inhale>
<deep exhale>
So here I’m going to try and explain in terms that are easier to understand than a college physics textbook how sound proofing actually works and why it’s more complicated than we think it is. Because it is. No, it’s not fair, but that’s where we’re at.
Those leaf blowers aren’t going to go away and sometimes actual legitimate sound proofing is required. It ain’t cheap, but it IS doable.
I’ll try to condense. This is already too long of a read!
How sound proofing is different from sound treatment
In short, sound treatment does not require sound proofing to do its job. Its job is to treat a space so that it will sound good. Or dead. At least passable for recording and mixing purposes. Or movie watching. Or whatever.
A sound proofed room will still need sound treatment! If you build a PERFECTLY isolated room, it’s going to have untreated walls most likely. Gotta do something about that so that your completely decoupled room doesn’t sound like the bathroom you just escaped from. Just because you can’t hear anything coming out of the nearby bathroom in that perfectly isolated room doesn’t mean it doesn’t sound like the inside of one!
You can see how this all starts to add up. And we haven’t event gotten to construction.
Do I actually NEED sound proofing? And if so, how much?
That’s the question that should be asked prior to doing ANYTHING outlined in this section.
Sometimes the answer is yes. You are a recording artist who needs a silent space at all times. Airplanes and lawn mowers are the bane of your existence and interfering with your livelihood. Under these circumstances, the answer is yes.
How MUCH is needed? That is the operative question and it will depend on each and every person’s very specific situation.
The first thing that should be done is acquisition of an accurate decibel meter. Yes, smart phones have ok ones in the form of apps. If you’re going through the process of building a space, it behooves you to get something designed specifically for that purpose. Use that decibel meter to find out what the loudest sounds you will experience on a day to day basis are. Once you have that measurement, the design process can begin because you know how much sound you need to block out.
On to even deeper concepts!
Mass, Air, Mass
Which sounds like a flight program or a workout plan, but it’s actually a concept that is part of what makes sound proofing possible. Have you ever heard loud construction happening out of your place of living? Have you ever gone to the basement or a central room in the same living place and found that it’s not as loud as if you’re standing near the front door? The reason this is possible is those sound waves have to travel through more mass and air to get to you in those other locations. The airplane going by above? The sound gets filtered through the density and air of where you’re at to get to you.
For studios, you have a mass of some form in the shape of walls or concrete or something constructed. An air gap filled with insulation acts as a break between an external room and an internal room. For mass air mass to work, you’re literally building a room within a room and it works. Really, really well.
Decoupling the walls
The mass air mass example is one of the ways that you can decouple a constructed space from the outside world. Sometimes you’re able to build a ceiling in this space that is completely unattached to the structure above and follow the same rules as the walls; the ceiling above as a mass, insulation air gap, and the ceiling below for your space. If you’re in a basement of a high flight area, having the top of your recording space decoupled from your main home structure solves that problem brilliantly.
Let’s say you’re in a basement and available height is extremely limited. If you try to build a ceiling that is detached with an air gap, you might not be able to stand up straight in the room you’re building. Which is inconvenient because we’re not hobbits. If you just attach your ceiling drywall to the joists above, you’re going to hear every single thing above you. Every footfall. Each drop of a Lego. Someone not using their CPAP. E v e r y t h i n g.
The solution? Decouplers! There are a variety of products that will allow you to attach drywall to joists above in a fashion that decouple and potentially eliminate sound transference.
Floating floors
I …. really hesitate to get into this one.
Partially because the need for floating floors is very rarely actually there. And partially because the process of calculating for and construction of a floating floor is excruciatingly complicated and VERY expensive. There are several OTHER ways to solve the problem of sound transmission through a floor that are best to consider prior to going through the floating-floor process. But for the sake of completeness, I’ll go over the idea.
The floating floor isn’t actually “floating” in the sense that we would think. There’s no water involved. This is more along the lines of having a thick concrete slab that has been decoupled from the floor below using a multitude of very thick spring mechanisms. They have to be just springy enough to absorb most of the sound coming through but not too rigid otherwise they will just transfer the sound. Think spring shocks on a vehicle that keep the vehicle from vibrating annoyingly.
Myth busting: plywood on top of 2x4s resting in rubber U-boat tracks is NOT floating the floor. Just like adding foam to the walls is not sound proofing.
Here’s another complication: the resonant frequency of the floor needs to be calculated in such a way that it is at a level that is below the threshold of usable sound. 15hz is as HIGH as you want that frequency to be.
Just for giggles, if you want to see what a properly constructed floating floor looks like, you can click on this link to get a look. It’s pretty, it works, and it’s COMPLICATED. And expensive. If you’re already at this stage, the person you’re working with to design your space is already telling you that you need it done because you are in a unique position where there is no other option.
Freestanding options
Double and triple layers constructs of booths and rooms are definitely viable options that will do a much better job of reducing – and potentially eliminating – external noises. Studio Bricks rooms are very popular for this purpose in that they come in multiple layers of thickness and are a proven entity. They are also WILDLY expensive at the higher tiers.
Do they work? You betcha. Can you roll your own actually sound proofed recording space for fewer earth dollars? Debatable. Potentially, yes. There’s an argument of “what is your time worth?”
My counter argument to that would be “not everybody can be their own handyperson contractor and build their own recording space.” It has to get contracted out for so many people. After getting a quote, it’s time to decide exactly how affordable some of those options actually are. Your mileage may vary.
Finality
So, a previously covered topic with even MORE WORDS is complete. I totally get that this is not everybody’s cup of tea in terms of subject matter. The previous entry on this subject might be more up the alley because it’s shorter and less statto. I want to believe that somewhere out there is someone who REALLY wants to know why their egg carton wall hangings aren’t going to do much good to keep the sound of the local construction vehicle artery roads out of their ASMR recording efforts.
Also, if you’re making enough money doing nothing but ASMR recordings that you can afford a floating floor, I really need to reconsider my career goals.
In the event that you’re still with me, if you want to review a very comprehensive document on recording studio building written by an exceptionally gifted studio designer in the late John Sayers, get ye here. I don’t expect anyone else to be as niche nerd about that as I am but it’s a VERY educational read.
That’s it for this topic! It’s a LOT. Then again, rumor has it so am I. Knowledge for the sake of knowledge is fun sometimes, right? I love sharing and hopefully this has been useful to someone! Please write and let me know if I missed something that you need to know more about or if there are any corrections to be made. The keto-compatible fatty computer made of meat inside my skull is hilariously fallible and I’m always open to adjusting what I know and share.
And besides, it’s fun to correspond, right? I promise not to send you several thousands of words in response. That would be cruel.
Yes, really.
Pinky promise.
…… unless I need to.
Until next week!
-= george =-
