Vocal Sound Booth Whisper Room Build: Part 5 Exhaust Baffles

[@sam24bit]

first time i am seeing so much hard work being concluded as a fail by the creator, you are the real deal man

[@themusicofmikegoodwin]

Eric, Thanks so much for your hard work in this series of videos. I love that you have shared your success as well as your failures. This is an invaluable tool for us all trying to build our own booths.

[@rascrr]

Thanks for sharing this “fail“ with us. It‘s not only the wins that bring us forward.

[@EricStrebel]

Yup, I agree! different fans are the answer probably here

[@grantpajohnson]

I built a small booth too and had the same disappointing fan noise issue. bought an inline AC type fan but they are just too loud. I even moved the fan to a place across the room and used a long long 6" AC tube. The speed of the air creates noise in the tube due to the rumbling air currents and friction like a fast moving car does. The right solution is a bigger fan, moving at slower RPM, air moving 4 times slower in a tube or composite set of tubes that creates 4 times the volume. Having four or more inlets and outlets to spread the volume of air to slow the speed and an increased "net" diameter composite set of pipes to reduce the additional noise that happens just from air friction noise on the walls of the portal connections.

[@musicoctavemotivation3720]

I know I'm late but another option is decoupling the boxes I know you mentioned that in the end. Either way you will figure it out. Awesome build as well. I'm building one inside my room. It's been very challenging. Appreciate you for sharing this with us. Keep up the good work 😉

[@unionse7en]

shag carpet works really well inside ducts, I mad an air compressor enclosure that works well. The shag elements "fingers" work probably better than a smooth surface for flow situations

[@EricStrebel]

Oh, that's an interesting idea!

[@SymetricalParadox]

Not sure if you're going to read this, but to reduce the noise you should try building a baffle with a much larger fan that moves slower. The larger fan will move the same volume of air as the smaller one but at a slower speed.

[@EricStrebel]

Ok, good idea

[@michaellyons5208]

Also late to the party, but keeping the source of the vibration as far from anything resonant is also a good idea. I wouldn't ditch the baffle boxes, but what I might do is pull the fan out and build a small, baffled separate box that sits away from the booth, connected by insulated duct to the boxes. Set the little fan boxes on a piece of carpet. Just an idea for folks considering options.

[@derkhedemann5606]

I bought this ventilation system for my vocal booth. Sonair Silent Ventilation unit and it is really super quiet

[@EricStrebel]

I will investigate

[@adventuresincampingwithcar8622]

When an installer of HVAC wants to deaden the sound of air flow. They insulate the outside of the pipe and leave the inside bare. As it allows the air flow to flow without hinderence. Anything inside, will cause turbulance, and turbulance causes noise.

[@MrSilver708]

I know this is real late but Noctua fans....they are the best...check them out its what I used on my booth and computers too. Happy New Year 😃

[@garagemonkeysan]

Nice video. Awesome you produce and post the "fails." Mahalo for sharing! : )

[@gurubuzzzz]

PC case cooling has evolved to silent cooling. They have high efficiency fans that run at low rpms. The fans are brushless PWM controlled and some of the higher end ones don't even have bearings, they hover in a magnetic field. As a bonus some have RGB LEDs, if you're into that 3 - 4 fans running at Low Rpm is the way to go. Also decouple your fan boxes from the booth, use non hardening glue/sealer and avoid screws, bolts and nails. Also blowing air with passive extraction is easier then sucking out.

[@gurubuzzzz]

I also had my inlet fans at floor level which takes the coolest air in the room, this way you don't need as much flow to keep cool thus reducing the rpms needed and lowering fan noise.

[@Holliwoodtay1977]

Try moving boxes off of booth on a rack 2 to 3 inc. away

[@JohnnyRock]

Noctua fans are very quiet and efficient.

[@RayoBeatz]

the fan blades need to be sound proofed and so does the box you also need an exaust in another part of the booth and an intake someplace else possibly air coming in from the bottom to the top and air coming out from the top to the bottom

[@EricStrebel]

Ok, thanks

[@granddesi2]

Hey bro, add a shop vac filter or hi flow automotive air filter somewhere inline.. nice to filter the air as well as cut back on sound... obviously will cut back on cfm but if you think about it, the slightest air flow is all youll need

[@majesticsuntravel9807]

Try to get some duct coils to connect to fans but have them bend 3 or 4x as sound doesn’t like to make turns. It will quiet the noice and possibly eliminate it.

[@GrandmasterofWin]

I'm a little late to the party, curious what you've come up with since this video came out. If you haven't looked into it any further, you might want to watch the whisper room factory tour. It's a 30 min video and it shows the full construction of their booths including the air ventilation system. It's similar to yours but instead of snaking tubing in an s curve with baffles at the end they have a long u-shaped box lined inside with tight knit carpet (incredible stuff for acoustics), but the secret is the box has curved foam wedges lining the sides that are shaped a bit like the curvature of an airplane wing. The whole thing reminds me a bit of a Tesla valve, however I doubt they are designed the same way for obvious reasons. Anyway, I believe the air bounces back and forth as it snakes through the box and exits the vent apparently silently. Oh, and instead of both push and pull, they only use a fan to pull air out. The vacuum created brings in fresh air.

[@GrandmasterofWin]

Oh and if you're curious, just search "whisper room factory tour" and the ventilation system is shown at 22:40. And at 20:40 they give a glimpse at the "foam baffles". I'm not great with terminology but yeah it's worth seeing to benefit from their engineering time.

[@compteyoutube8421]

Hi ! Why not simply power off the fans when pushing on the record button; and get back the fans powered on when the record stop ?

[@EricStrebel]

Well, that's not a half bad idea actually.... I will give it some consideration

[@wandering-mystic]

@@EricStrebel We do it all the time during film production. Shut off all A/C and/or fridge compressors. However, if you're recording for extended periods, you'll need to take breaks to ventilate and cool.

[@spencermiles963]

Also using rockwul around the tubing in your fan box would further silence the box.

[@choiceblade]

Foam buffer the contact patch of the fan box on the outside wall. Even mounted it should be significantly quieter?

[@jasontsh]

You need to not only decouple the boxes from the booth, but also decouple the fan units from the boxes, as the vibrations are resonating the boxes, then resonating the booth itself. Fan noise is being transmitted directly through the structure. The other thing is, your boxes need to be like a maze, with walls inside, rather than just a big open box with a bendy duct in it. Every time the ducting doubles back against itself, there needs to be an MDF wall there, stopping the airflow sound just going out the side of the ducting, into the ducting next to it. Without the walls of the maze, the sound just gets straight from one end of the box to the other, albeit a bit dampened by the ducting's insulation. Message me if you need me to explain further. :)

[@jasontsh]

One more thing: You're better to have a slightly positive air pressure in there. Which means that you need to be pushing a bit more in that you're pulling out. At the moment, you're not pushing any air in at all, and only pulling it out. Try pushing air in at the bottom of the booth, instead of pulling it out at the top. Firstly, the holes at the bottom of the booth are physically further away from your mic, so that in itself may help reduce the sound by a few dB. Secondly, it'll just feel nicer in the booth with a slightly positive air pressure. You may then need one low powered fan at the top, to help pull the air out.

[@EricStrebel]

Thanks

[@arrangemonk]

noctua fans are pretty quiet

[@ivalice09]

Have you considered doing a price breakdown of the unit in a video? Or a parts list? I’ve been working towards building one of my own. Thank you. I like your videos!

[@EricStrebel]

Nope, I have considered it

[@ncQuadrat]

I would consider experimenting with a different fan diameter as this affects the rotation frequency per minute and with that the noise generated by the blades, also check out ebmpapst fans, they have decent data on their fan noise levels. Besides that i see a lot PC-Modders use noctua fans for ultra silent cooling, maybe you could get some inspirations from their fan blades

[@EricStrebel]

I have watched a few videos about those fans it's on the top of my list

[@0xBytes]

You could try adding a reflector to the mic stand this should cut all noise coming from behind the mic, not really a solution to still hearing the fans problem

[@sam24bit]

have you tried decoupling the fan itself from the booth using a hose pipe? is the fan being connected to the entire structure causing some structural vibration?

[@EricStrebel]

No, but it think it would help!

[@hblomqvist]

“Years ago, we started redistributing the blades ,” he says. “They’re still dynamically balanced, but they’re actually randomized in terms of their BPF [blade pass frequency]. So you don’t get huge harmonics that tend to be super annoying.” Noise is a major factor in the design of modern machinery. In this case: “That [solution is] borrowed almost entirely from automobile tires,” Ligtenberg says. “There’s a bit of math behind it, but you can create broadband noise instead of total noise with that technique.” Something loud but pleasantly pitched can be more tolerable than something quiet but irritating. “You can have something at a certain SPL [sound pressure level] that sounds really good, but you can have something that’s actually at a lower SPL that grates on your nerves and sounds really awful,” says John Ternus, VP of Hardware Engineering at Apple and head of the Pro and Pro Display’s development. “We want to get really great performance where, you either can’t hear it, or if you can hear it, it’s kind of a pleasant noise. A ton of analysis goes into figuring out how to optimize for that.” Source: 9to5mac.com/2019/12/12/mac-pro-fans/

[@EricStrebel]

Yeah there's a lot of truth to that

[@SianaGearz]

This whiny pitched behaviour PC fans used to have 20 years ago, it has gotten much weaker and nicer noise shaped. I think Taiwanese OEMs have started doing exactly that - perhaps even accidentally to an extent - a good while ago, more than 10 years ago. The only cases when i have heard distinctive pitched whine from a fan since was due to an unfortunate intermodulation between the PWM control and the fan's internal winding switch rate, which is more on the mainboard designers, since they have the tacho feedback and they know that the switch rate must be a whole multiple of that, so they would have had a way to avoid it. I think Apple is slightly exaggerating its accomplishments for marketing purposes, or potentially ascribing itself accomplishments that aren't even theirs to begin with, but the general wind of the industry.

[@EdTheBearsFan]

Thanks for sharing! I bought two Noctua fans for my booth that I’m building: Noctua NF-A12x25 FLX. Also, have you considered adding a couple of layers of the MLV between the vent box and the booth?

[@EricStrebel]

Thanks for feedback, and information

[@hepkids3255]

Use NS1 Noise Suppressor little bit.

[@EricStrebel]

Please elaborate... thanks

[@hepkids3255]

@@EricStrebel Vst plugin from Waves. You can completely eliminate the bottom noise with a small touch.

[@EricStrebel]

Ahhh, I c. Thanks

[@hepkids3255]

@@EricStrebel Trying to fix everything the old fashioned way is insane! Digital solutions for digital recording should also be explored. I thank you :)

[@MagicCyclops]

Vocal booths to go I think sells quite fans . But just look how whisper room does it is stupid simple maybe you over thought it. I do that a lot myself

[@Nocholas]

Just by a used airbox for a vehicle and make your mods from there.

[@EricStrebel]

Interesting idea

[@SianaGearz]

The swipe at game streamers was unnecessary and uncalled for. The vast majority do this as a hobby and don't receive a significant income, they come home from a job in the evening and join maybe an audience of 10-30 people, and i think they perform an important function in society especially this year now that most social activities are no longer available. Those few that are successful enough to make a living out of it, they are essentially public entertainers, and have to manage and entertain an audience, and that's immensely stressful - and i know, i look at some of them too and find they're shit at what they do, but you know, there are always some of those people, i'm sure not every popular and successful product designer is actually known for excellent work, and i actually have a name in mind but won't say. I'm sure you wouldn't appreciate someone making swipes at what you do just because it's usually not physically stressful either, or because there are a handful people who deliver ridiculous broken shit and are celebrated for it. Fans? Nothing beats Noctua. Unfortunately... can't quite recommend, and that's not because of the quality, it's great. Don't even go comparing the specs, because you simply can't trust the airflow and noise measurements from any manufacturer, all are differently cheated, none make sense. For the same level of airflow in any practical setting, you generally get the same level of air noise from just about everyone. Noctua does slightly better than the rest, but if the existing fans are audible, then likely Noctua will still be audible, the issue appears to be more fundamental. You don't have motor/bearing noise for example, which if you had that, replacing fans would have made sense. But the air noise is simply inescapable, you can only improve on it slightly by going Noctua. Don't even bother. You have a handful little holes and a transmission line, known from speaker design, which is a difficult thing to get right. Unfortunately i don't have a solution off the top of my head. I'll try to think of something but can't quite promise. As you can imagine the things that i know from acoustics to stop the air noise tend to do a whole number on straight up airflow, it's actually way easier to stop the airflow than it is to stop the sound. Sound is extremely resilient.

[@dmay3391]

"The swipe at game streamers" my my... aren't you fragile. Why does mommy let you use the internet?

[@SianaGearz]

@@dmay3391 It's not about me. I don't need to feel bad for standing up for someone else. And what good deed have you done today or this week? For example i helped someone i didn't know set up a reverse engineering project on an old piece of electronics, and they had the first result just today. Is denigrating other people your purpose in life? Does it make you happy? Is it worth living a life like that?

[@dmay3391]

@@SianaGearz You've demonstrated fragility, the opposite of standing up. Pathetic. I don't understand how mommy isn't pulling you back from the monitor right now.

[@EricStrebel]

@D May, Chill bro, just chill...her comments have 7thumbs up right now, that counts for something, she is trying to add to the community, she is entitled to her opinion, all good.

[@SianaGearz]

@@EricStrebel So here's my additional thoughts. 1. Two 12cm fans probably aren't nearly enough. A human can be expected to expel only slightly less heat than a gaming computer, probably around 130W, computer closer to 200W; and you could just about cool such a 40-50 litre computer with two 12cm fans without generating too much noise. However in a computer enclosure, 40°C is specifically the design target, but such temperature would be remarkably ill suited for a box with a human in it. So you probably want more airflow, more fan area and more ventilation opening area. 2. It makes sense to locate the source of noise as far from the microphone as possible, i.e. have active air intake at the bottom of the cabin, and the covered walls of the cabin will hopefully absorb most of the noise before it hits the mic. You may also keep convection direction in mind, that as the air is heated up by the human, it will rise to the top. Normally in a PC you ignore convection as the active airflow overpowers it by an order of magnitude, but i'm not convinced that it can be ignored in a human sized container, because the fan air velocity gets distributed over a large area. I found some website with a rule of thumb formula that gives me rough convection flow figures off a person on the order of 0.1m^3/s volumetric or up to several m/s linear - something doesn't add up, so i wouldn't really believe them for a second, but these are scary large figures. Silent 12cm fan spec is like 0.01-0.02m^3/s, that order of magnitude. In fact if the convection figure is anywhere near close to true, fans might turn out to be entirely useless? Though they do create a pressure differential, so might be good in this regard, but very little at low RPM. Also, one side of the air path is currently behind the LCD near the top of the cabin, but where is the other side? If you think the air will make its way through the door jamb as needed, well that won't really happen because the narrow slit is an airflow impedance, and you don't really have a powerful enough source of static pressure to overcome it, and you probably won't as you're trying to make it low noise. Remember you're not literally adding or removing air by a fan, you're flapping at the air with your lil blades hoping it'll go somewhere where you want it to, which it very much might not, depending on pressure relationships, in fact i've even seen airflow flip completely the wrong way around just from putting a funnel on fan's outlet :D 3. Circular apertures are best avoided, they have a resonant behaviour. Sharp corners can be a source of noise too, but that's not the problem at the moment. So pipe was probably not great. The surface of the pipe was not coated with anything absorbent, so there's not even a point to it, it just conducts the noise from one end to the other along with the air. You may think that you can attenuate noise with distance, as the sound pressure falls with the square of distance; however this attenuation occurs purely out of a geometric consideration, that with larger distance, the same sound energy is spread over a larger area as the spherical sound wave surface expands from the source outwards, and this is valid specifically in free air. In narrow confinement, where the sound is reflected off the walls, this is not the case, in such volumes there is no distance attenuation, as you're folding back the same energy onto the same crossectional area, but you do have added resonance, and added air friction noise, when air moves along the surface, some of its velocity will be converted to noise, so ideally you want the air to travel along as little surface as needed. It would probably work better to just have the air box with covered inner walls and some kind of also covered barrier structure within the box that avoids repeating and regular dimensions, to help sound bounce off foam or loose fibre material multiple times before it arrives at the destination, every bounce absorbing some of it. 4. Take polar signature of your microphone into account. You had built a ribbon microphone previously, right? I think it has figure of 8 pattern? So the top and bottom noises in the plane of the membrane are rejected strongly. If you have a cardioid microphone, you point it with its back directly towards the source of noise for highest rejection ratio. If you have a supercardioid microphone, you take the specific null angle from its spec. 5. Ask around whether you have a friend of a friend who is a HVAC engineer. Air ducts and noise suppression in these are their bread and butter! They'll know things the rest of us don't. As an aside, is "D May" a friend of yours? Or someone you'd be proud to call your friend? Not that i really care to know, just for your deliberation.

[@MeTuLHeD]

Hey man. Since you don't require your booth to be soundproof, why didn't you just leave it open on one end? That way you would have had airflow and still would have gotten the benefit of the treated walls killing reflections. You wouldn't have had to deal with ventilation.

[@SunnyMoonProductions]

Could you not find a fan that makes less noise?

[@TavardoReasias]

The fans are pretty quiet, its not a bother at all.

[@MrFaaaaaaaaaaaaaaaaa]

Have you considered selling these? I seem to recall a certain someone in the EPA paying 43,000 taxpayer dollars for one of these booths to be installed.

[@EricStrebel]

Sure

[@majesticsuntravel9807]

Hi Eric. How much did it cost to make? How much would it cost you to make from specs? I could drive from Cleveland to pick up if I decide to purchase.

[@acerecords3290]

Hello, I recently seen your video build for a audio recording booth and I wanted to know if I could pay you to build another one. I live in Windsor Ontario right across the border from you and I'm willing to pay for all the materials used whether 3d printed or not. Also just as a little bit of extra comfort for you that you will be paid for your hard work we can put the entire build under contract. Please let me know I would absolutely love if you could do this for me.

[@EricStrebel]

Contact me through my web site and let's see if we can work something out www.botzen.com

[@jafinch78]

Amazes me there are University degree programs in just playing video games and even related to playing video games other than the business aspect programs. I don't like fiberglass... though man... seems like some foam and glass or even like heat gun and wrapping a mold with HDPE or PVC maybe then plastic welding if needed? Acoustiblok commercials reigned for a while with me on YT and there is a Acousti Mat also I've seen. Get's me wondering about 3D printing materials that are optimal, metamaterial surface design for the inside and even lining with foam or whatever the material with cones? Noctua I recall being the quietest fans. I don't know... comments help metrics though.

[@EricStrebel]

What? There are degrees for playing video games? WTF? People pay money for that, seriously? That's messed up! Thanks for your support! I am looking into quite fans

[@jafinch78]

@@EricStrebel Yeah, I was at the Maker Space in the Waldo library at WMU like last year at one of the meetings and I didn't believe when I first heard em talk about investing in the courses. Was like WTF also? Even Tech is doing something... though more rational, like "esports" and I'm even amazed at all the game design programs since seems scammy also. Like gambling degrees or something will be next. Isn't helping society and U.S. jurisdiction metrics for sure. Seems better and more constructive or maintaining acts to do to stay out of trouble and spend time.

[@SianaGearz]

@@EricStrebel people come up with shitty rumours just to have something to be outraged about.

[@shadeofbrownpod]

Noise gate plug in 🤷🏽

[@sinofusall2080]

lol just install a Cloud line fan like 5 feet away Noise solved and plenty of Air flow

[@EricStrebel]

What is a cloud line fan

[@sinofusall2080]

@@EricStrebel a simple google search will show results sir, but in any case www.acinfinity.com/

[@EricStrebel]

That's basically what I already have, lol

[@sinofusall2080]

@@EricStrebel there built for quiet, i was thinkin instead of having the exhaust hooked up to the unit you would rather have it seperate and on the side. that way you will have no noise from any blades and only air pushing or pulling. those fans you bought from amazon are def not what you want in a luxury build such as this lol

[@sinofusall2080]

@@EricStrebel check out the duct fans

[@philipdahl8767]

the sound comes from the vibrating fan and not the airflow and you should work on the connection they are making with the booth and dampen those.

[@EricStrebel]

Yes, I do believe that is part of the issue, the MDF of the vent box is probably conducting sound through the screw mounts into the booth. The other is the fan probably needs to have some dampening on the connection to the box as well. I will probably have to crack open the box and make some adjustments. I will probably swap out the fans at that time. Thanks for your feedback. Much appreciated

[@gon2u38]

@@EricStrebel yes I now understand the rubber stretchy plugs where you ended up screwing them. See if they are ok to use and remove your screws. Also, if you can DECOUPLE THE FANS THEMSELVES from the box you should be able to eliminate the fan noise altogether. Have them free floating with simply lightweight plastic vent tubing so it doesnt transmit any vibration noise which is what I found I got. Your baffles should have cut all the air flow noise down already. It won't take much to make this project perfect. You CAN'T QUIT NOW DUDE!!!

[@ImageforgeAsia]

Have to say it sounds boxy... you need thicker bass traps imo, either thicker foam all around or especially in the corners some extra thick foam/pillows etc. Can also use a filter for frequencys below 100 hz which will help :) Awesome build though, just think it needs a little more treatment

[@mekaylaskye]

try some fiberglass

[@EricStrebel]

Hate the stuff, thus the foam, works great

[@joeltham1979]

They don't sound any different to me.

[@poorkidd]

Don’t discount the hand eye coordination, team building “ working with others to complete a goal”, and problem solving skills game offer.

[@EricStrebel]

Lol

[@anointed01]

Try a dynamic mic, like the Shure SM58

[@GrandmasterofWin]

I know this is an old comment and that the guy who built the booth knows better, but for anyone who reads the comments from here into the future, a dynamic mic is a bad idea and would negate the entire purpose of an iso both. Sure, a dynamic mic would pick up significantly less room noise and would take more abuse and put up with louder vocals before distorting, but the recording would lack the fidelity of a large diaphragm condenser mic. A dynamic mic is great for live stage performances but is a waste when used in a treated space for voiceover or singing. It's the sensitivity and clarity of a condenser mic that leads people to build booths in the first place. There's a reason nearly every radio DJ uses a condenser, why nearly all voiceover artists seek a condenser mic, why nearly all album vocals are recorded with condensers and why every professional studio has a selection of condensers, also why a good condenser can be anywhere between $300-3000 instead of $80-130. Dynamics are great for what they are, sturdy knockaround devices for the road, rock and rap performances and more, but they are usually not the right choice in a studio and almost never the right choice for an iso booth.

[@EricStrebel]

Yup