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How to get air in and out of the studio without noise Effects Pedals, Units & Accessories
Old 15th May 2018
  #1
Gear Maniac
 

How to get air in and out of the studio without noise

So I have been researching the concept of HVAC and trying to figure out which system is best for a basement studio. Ductless mini split systems are pretty much the norm around these parts but they don't get fresh air in and out of your recording space which is a problem. After speaking to several HVAC guys about the best way to ventilate my studio this idea was proposed and wanted to run it by the forum to see if I could get some advice from you folks about it.

So, the proposed ductwork will run above the false ceiling as in diagram "1" (it is the one on the left), or within soffits in the corners of the room as in diagram "2" (it is the one on the right). There will be one duct on each side of the room, one for supply and the other for return.

I am obviously a bit worried about sound traveling through these ducts from the fans or from outside. According to image 2 (which I got from a soundproofing company) the PVC ductwork used is transparent to sound so the fiberglass around it in the soffit absorbs it thereby reducing transmission to other end. Is this correct? What other techniques or solutions are used to correctly ventilate a studio without sound leaking through? I have read that you can also use absorptive foam within the ductwork so long as the material used is apt for the application (obviously fiberglass will be a no no)

I am still a beginner with HVAC so please correct me and I look forward to chatting about this

thanks!
Attached Thumbnails
How to get air in and out of the studio without noise-1.jpg   How to get air in and out of the studio without noise-2.jpg  
Old 15th May 2018
  #2
Gear Addict
 

From your diagrams it’s hard to get an idea of the engineering you’ll put in to create the ducting. If you were to simply run flex duct from point A to point B you could have some issues.

But that being said, running the ducting through the ceiling/soffits/walls is how almost all studios are built. You just need to do some reasearch on how to mitigate any noise issues. There are lots of good ideas out there. Search google for terms like “dead vent” and “duct silencer.” You’ll get some ideas.


If the partition above the duct (the floor I’m guessing) is reasonably sturdy, your real only concern for noise entry might be where your duct connects to your fan, or penetrates to the outside to exhaust. If the floor is thin and transmits voices and footsteps easily, you may need to engineer something a bit more isolated.

Here’s another thing to remember, and something I keep reminding myself of as I’m building my own studio right now (I have a build thread you can probably find): unless you have deep, deep pockets, it’s never going to be perfect, and that’s okay. Music is my full time job, no other sources of income. I’ve been able to make a career out of it working in extremely imperfect spaces. In my last studio the main tracking room had huge bay windows that looked out over a street. Any time a big truck or motorcycle drove by it would bleed through. The next door building had 3 AC units in the alley between us, and in the summer they all 3 ran so loud. In the control room you could hear birds chirping outside. I worked in that space 3 years and made a lot of records there. I did production, vocal tracking and overdubs on a Grammy nominated record, scored a feature film that killed the festival circuit and got picked up by Netflix, and recorded songs that were licensed for big TV shows and national commercials.

The tracking room never sounded perfect. The isolation was awful and the control room was a disaster (thin floating wood floors, essentially I sat on a reverb tank). I did great work in there. So any time I start obsessing about if my ducting will be too loud in my new spot (after I’ve already taken huge measures to ensure it’s as quiet as possible), or other similar isolation or acoustic issues, I just have to remind myself it will be many times better than my last space, and my last space never held me back from making music and records I was proud of.
Old 15th May 2018
  #3
Gear Maniac
 

Quote:
Originally Posted by logjamparty View Post


If the partition above the duct (the floor I’m guessing) is reasonably sturdy, your real only concern for noise entry might be where your duct connects to your fan, or penetrates to the outside to exhaust.
Thanks for your post. Yes this is the only concern I have. I am worried about noise coming in from outside through the ducts or the sound of the fan coming through the ducts into the room.

Good to hear your experiences and that you still made good music despite imperfect workplaces. That is inspiring. I would like to make mine as best I can though so still looking forward to hearing some more great advice

thanks again!
Old 15th May 2018
  #4
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Starlight's Avatar
Search the forum for the word baffle to find a PDFs, drawings, photos and descriptions of how others have made baffle boxes, silencers, for our ventilation systems.
Old 15th May 2018
  #5
Gear Addict
 

Quote:
Originally Posted by eljefe View Post
Thanks for your post. Yes this is the only concern I have. I am worried about noise coming in from outside through the ducts or the sound of the fan coming through the ducts into the room.

Good to hear your experiences and that you still made good music despite imperfect workplaces. That is inspiring. I would like to make mine as best I can though so still looking forward to hearing some more great advice

thanks again!
If you want more advice you have to give more info. Your post doesn’t really say anything. You want exactly what we all want. It’s just that every single build has different hurdles to overcome.

How is the ceiling above the false ceiling? How is it constructed? Is the false ceiling truly decoupled? Do you need to decouple it? Is the original ceiling itself insulated both thermally and acoustically? What’s above that? How much space is between the the two assemblies? What’s the construction of the false ceiling? Is the false ceiling even in place or is that something you plan to build? If it’s already built did you take measures to make sure it was isolated from the floor above it? You could have perfectly isolated ducts but if the ceiling, floor, and walls of the basement aren’t isolated from the rest of the building, money spent on isolating HVAC is silly. The sound coming through your ducts is secondary to the sound coming through your structure.

How much air do you need? What’s the cfm of your fan? Do you want balanced ventilation? Positive pressure? Negative pressure? Have you considered the air you’re introducing to your studio, ie, if you live in a somewhat humid climate, or a climate with severe summers or winters, you’ll want to look at an ERV/HRV to temper your air before you dump it in to the studio. Where you place your supply is important in relation to your mini split, mine dumps directly above my split to condition the new air immediately.

Based on how much air you need you’ll need to size your ducts, silencers, supply and return, to have a low enough velocity to be silent coming in and going out. Obviously the area you have between the partitions will determine part of this.

There are a hundred things to consider and no one can really give you advice because you haven’t really given enough information. It’s like walking in to a car dealership and saying: “I want the best car you have.”
That could mean something totally different for a soccer mom, a construction worker, and an off road enthusiast.

Figure out your exact needs in terms of isolation, air flow, ventilation type, then figure out the budget you have to accomplish them, then determine the construction parameters you have to work inside. At that point people could give you some advice.
Old 16th May 2018
  #6
Gear Maniac
 

Quote:
Originally Posted by logjamparty View Post
If you want more advice you have to give more info. Your post doesn’t really say anything. You want exactly what we all want. It’s just that every single build has different hurdles to overcome.

How is the ceiling above the false ceiling? How is it constructed? Is the false ceiling truly decoupled? Do you need to decouple it? Is the original ceiling itself insulated both thermally and acoustically? What’s above that? How much space is between the the two assemblies? What’s the construction of the false ceiling? Is the false ceiling even in place or is that something you plan to build? If it’s already built did you take measures to make sure it was isolated from the floor above it? You could have perfectly isolated ducts but if the ceiling, floor, and walls of the basement aren’t isolated from the rest of the building, money spent on isolating HVAC is silly. The sound coming through your ducts is secondary to the sound coming through your structure.

How much air do you need? What’s the cfm of your fan? Do you want balanced ventilation? Positive pressure? Negative pressure? Have you considered the air you’re introducing to your studio, ie, if you live in a somewhat humid climate, or a climate with severe summers or winters, you’ll want to look at an ERV/HRV to temper your air before you dump it in to the studio. Where you place your supply is important in relation to your mini split, mine dumps directly above my split to condition the new air immediately.

Based on how much air you need you’ll need to size your ducts, silencers, supply and return, to have a low enough velocity to be silent coming in and going out. Obviously the area you have between the partitions will determine part of this.

There are a hundred things to consider and no one can really give you advice because you haven’t really given enough information. It’s like walking in to a car dealership and saying: “I want the best car you have.”
That could mean something totally different for a soccer mom, a construction worker, and an off road enthusiast.

Figure out your exact needs in terms of isolation, air flow, ventilation type, then figure out the budget you have to accomplish them, then determine the construction parameters you have to work inside. At that point people could give you some advice.
I was only asking for general advice on how to get a duct from A to B without sound passing through it into your studio.
Old 16th May 2018
  #7
Gear Maniac
 

Quote:
Originally Posted by Starlight View Post
Search the forum for the word baffle to find a PDFs, drawings, photos and descriptions of how others have made baffle boxes, silencers, for our ventilation systems.
thank you, found some good stuff there!
Old 16th May 2018
  #8
Gear Addict
 

Quote:
Originally Posted by eljefe View Post
I was only asking for general advice on how to get a duct from A to B without sound passing through it into your studio.
In a sound proof duct.
Old 17th May 2018
  #9
Gear Maniac
 

Quote:
Originally Posted by logjamparty View Post
In a sound proof duct.
yes ok perfect and thank you! So can we please discuss options for soundproofing the duct now? So the options I have found are

1) the silencer box where the duct is snaked through a box surrounded by fiberglass
2) there is a PVC duct that goes through a soffit as in the diagram in the OP

Are there any other options and are both of the above used simultaneously or are they two different methods?
Old 17th May 2018
  #10
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johndykstra's Avatar
 

Logjamparty gave you the info you need.

That is to say, it's not so simple. Too many factors at play to just give you a direct answer.
Old 24th May 2018
  #11
Gear Maniac
 

Quote:
Originally Posted by johndykstra View Post
Logjamparty gave you the info you need.

That is to say, it's not so simple. Too many factors at play to just give you a direct answer.
No there aren't too many at this stage. Since posting this I have studied this topic extensively and it seems like simple to-the-point- answers are all over the place. The question was simple: How to get air in and out of the studio without noise. The answer is also very straightforward:

1) use duct lining and low velocities meaning larger ducts
2) use a baffle box

Those are the solutions I was looking for, is that so difficult? Starlights response helped because he supplied the keywords i used to help find this information and logjams first post was also very helpful.

My question still stands in the sense that if there are other ideas that work please share/add them to my list!
Old 24th May 2018
  #12
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johndykstra's Avatar
 

you're a very friendly and patient person. best of luck to you on your journey
Old 24th May 2018
  #13
Gear Maniac
 

Quote:
Originally Posted by johndykstra View Post
you're a very friendly and patient person. best of luck to you on your journey
I know. Thank you
Old 24th May 2018
  #14
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Quote:
Originally Posted by logjamparty View Post
From your diagrams it’s hard to get an idea of the engineering you’ll put in to create the ducting. If you were to simply run flex duct from point A to point B you could have some issues.
The flex duct is surround by thick absorption so why would there be an issue? Flex duct can be very very thin plastic and sound waves would pretty much pass right through it into the absorption.
Old 24th May 2018
  #15
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I am reading "Build it like the pro's" by Rod Gervais which goes into this a bit (although not enough IMO) and he says that the big thing is to make sure your air is moving slowly within the ducts if you want it to be quiet. Run your fan on the lowest setting. You can also have a baffle on the inside of your room but you must make sure to make the baffle no longer than 3 times your duct size.
Old 24th May 2018
  #16
Gear Maniac
 

You could do something like this
Attached Thumbnails
How to get air in and out of the studio without noise-dead-vent-diagram-profile.jpg  
Old 24th May 2018
  #17
Gear Maniac
 

Quote:
Originally Posted by johndykstra View Post
Logjamparty gave you the info you need.
You are right I missed this gem right here:

Eljefe: How do you get fresh air in and out of the studio without the noise?
logjamparty: In a soundproof duct



that was just brimming with usefulness
Old 24th May 2018
  #18
Gear Maniac
 

Quote:
Originally Posted by attaboy_jhb View Post
I am reading "Build it like the pro's" by Rod Gervais which goes into this a bit (although not enough IMO) and he says that the big thing is to make sure your air is moving slowly within the ducts if you want it to be quiet. Run your fan on the lowest setting. You can also have a baffle on the inside of your room but you must make sure to make the baffle no longer than 3 times your duct size.
thanks! Does the size of the duct matter too? I read that you are better off with a larger duct but then my common sense tells me that a larger duct will transmit more sound. Am I wrong about this?
Old 24th May 2018
  #19
Gear Maniac
 

Quote:
Originally Posted by camomiletea View Post
You could do something like this
I like that but heres my question: is it possible to have a fan clogged up like that in the soffit, won't it not be able to stay cool? Also, don't you need access to the fan?
Old 24th May 2018
  #20
Gear Addict
 

Quote:
Originally Posted by attaboy_jhb View Post
The flex duct is surround by thick absorption so why would there be an issue? Flex duct can be very very thin plastic and sound waves would pretty much pass right through it into the absorption.

Your confusing concepts: insulation (fiberglass, mineral wool, etc) and how it relates to absorbing frequencies for creating a flat listening environment, and insulation and how it relates to sound isolation.

In creating a good sounding room, the insulation is simply absorbing those frequencies. It does nothing to stop them completely, except for very high frequencies. Unless you’re dealing feet of insulation, it will do nothing to isolate sound on it’s own.

In sound isolation the insulation is only a cog in the wheel of preventing sound transmission. The insulation in between stud cavities in a wall system serves to dampen the otherwise hollow cavity. The isolation comes from mass: the mutilple layers of drywall on either side of the insulation.

When isolating ducts, you’re not just trying to prevent sound entering your room from one end of the duct or the other, through the grille. Your duct is running through a wall or ceiling. Both sides of your wall system my equal STC 65, but in between the walls, who knows how much sound is in there! All that sound is then being transferred in to your duct and out the supply/return vents.

A grille is a giant hole in your wall. A duct leading to that grille is a giant funnel guiding the noise. You need isolation boxes or silencesers at either end. Better yet, run the ducts in soffits on the outside of the wall, or in hidden soffit between the wall to prevent sound leaking in over the, 10, 20, 30ft of ducting.

But. Again. Before you can do that you need to determine all the variables I listed in a previous post to ensure that you spend your money wisely and don’t end up over engineering and wasting money, or under engineering and ending up with something that needs to be fixed, which might require tearing out drywall.

Everyone wants an easy answer. But they don’t exist in this world.

Last edited by logjamparty; 24th May 2018 at 07:54 PM..
Old 24th May 2018
  #21
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Quote:
Originally Posted by logjamparty View Post
In sound isolation the insulation is only a cog in the wheel of preventing sound transmission. The insulation in between stud cavities in a wall system serves to dampen the otherwise hollow cavity. The isolation comes from mass: the mutilple layers of drywall on either side of the insulation.

When isolating ducts, you’re not just trying to prevent sound entering your room from one end of the duct or the other, through the grille. Your duct is running through a wall or ceiling. Both sides of your wall system my equal STC 65, but in between the walls, who knows how much sound is in there! All that sound is then being transferred in to your duct and out the supply/return vents.

I think if you look at the diagram again you will see that the soffit is on the inside of the room. The hole that penetrates the inner leaf is covered by the soffit so the only sound that can pass through the duct or the duct hole has to travel through the soffit and out the grill. When the sound is travelling along the duct, if the flexi duct is thin plastic, the sound will pass right through it and be absorbed by the absorptive material and be trapped inside the soffit. Sound energy is absorbed and turned to heat while the fresh supply air continues on its path to the grill and into the studio

What is wrong with what I have said?
Old 25th May 2018
  #22
Gear Addict
 

Quote:
Originally Posted by attaboy_jhb View Post
I think if you look at the diagram again you will see that the soffit is on the inside of the room. The hole that penetrates the inner leaf is covered by the soffit so the only sound that can pass through the duct or the duct hole has to travel through the soffit and out the grill. When the sound is travelling along the duct, if the flexi duct is thin plastic, the sound will pass right through it and be absorbed by the absorptive material and be trapped inside the soffit. Sound energy is absorbed and turned to heat while the fresh supply air continues on its path to the grill and into the studio

What is wrong with what I have said?
Nothing is wrong. But he posted TWO options. His idea and the soffit idea.

I addressed both options.

I don’t know why everyone fights the notion that there is a **** ton more to address here than sound isolation.

There are so many variables to consider that focusing on sound isolation is kind of silly. You NEED to figure out all the other details I’ve mentioned AND THEN once you have those figured out, figure out how to isolate what you need.

How big are his ducts? How much cfm does his fan push? How much friggen air does he need?? How many change overs does he want an hour? How much much static pressure can his fan handle before it starts droppig it’s cfm? Any idea of your target air velocity in the ducts?

You’ve gotta know all these things before you start designing sound isolation. You could design a great isolated ducting system and when you switch on your fan A) have whistling vents because you didn’t size your duct according to the air velocity, B) you could severely under supply the room because the fan wasn’t sized correctly to handle the static pressure of the duct work, C) you’re air change over is too great because you didn’t need calculate your needs before you started and you AC or heater can’t adequately cool or heat the room. You could run in to humidity issues, temperature issues. A lot of stuff.

Isolating a duct isn’t rocket science. It’s figuring out how to make all the variables work together that will determine if the time and money spent on construction was a failure or success.
Old 25th May 2018
  #23
Gear Maniac
 

Quote:
Originally Posted by logjamparty View Post
How big are his ducts? How much cfm does his fan push? How much friggen air does he need?? How many change overs does he want an hour? How much much static pressure can his fan handle before it starts droppig it’s cfm? Any idea of your target air velocity in the ducts?

Ok so I took the opportunity to do this now so we can get it out the way. My room is 4000cf and I will need no more than 2 air changes per hour. The formula as I have understood it is 4000 X 2 and then divide that by 60 to get the cfm figure. So I need to push 133cfm of air through my ductwork. The fan I am thinking of getting is this one

https://www.amazon.co.uk/Ultra-quiet...ent+inline+fan

The absolute lowest setting on this fan offers 206cfm
Sound pressure level @ this setting: 22 dB(A)
I am using 6" ducts

The static pressure is not listed but if the fan can offer 206cfm while I need 133cfm then I think there shouldn't be a problem.

If this information helpful, is there any other info I can provide logjamparty?
Old 25th May 2018
  #24
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Quote:
Originally Posted by logjamparty View Post

Better yet, run the ducts in soffits on the outside of the wall, or in hidden soffit between the wall to prevent sound leaking in over the, 10, 20, 30ft of ducting.
I don't see what difference it makes having the soffit on the outside. Perhaps you would like to explain why this is better?
Old 25th May 2018
  #25
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Quote:
Originally Posted by eljefe View Post
Ok so I took the opportunity to do this now so we can get it out the way. My room is 4000cf and I will need no more than 2 air changes per hour. The formula as I have understood it is 4000 X 2 and then divide that by 60 to get the cfm figure. So I need to push 133cfm of air through my ductwork. The fan I am thinking of getting is this one

https://www.amazon.co.uk/Ultra-quiet...ent+inline+fan

The absolute lowest setting on this fan offers 206cfm
Sound pressure level @ this setting: 22 dB(A)
I am using 6" ducts

The static pressure is not listed but if the fan can offer 206cfm while I need 133cfm then I think there shouldn't be a problem.

If this information helpful, is there any other info I can provide logjamparty?
Instead of running the flexi duct above the false ceiling why not create a soffit inside the room like in the diagram you posted. This is going to be better than just running it above the false ceiling because noise from above will get into the duct.
Old 25th May 2018
  #26
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Quote:
Originally Posted by logjamparty View Post
But they don’t exist in this world.
Unfortunately, you may be right but people in acoustics also are very good at over complicating
Old 25th May 2018
  #27
Gear Nut
 

@eljefe, from your amazon.co.uk link, am I correct in assuming you are in the UK? If so, by my understanding, UK building regulations stipulate you must allow for both purge ventilation (which I believe your fan solution will provide for) and also background ventilation of at least 8000mm2 equivalent area. If you are in a basement, I think the rules are slightly different, depending on the specifics of the structure. All depends how much you're sticking to regs though.
Old 26th May 2018
  #28
Gear Maniac
 

Quote:
Originally Posted by McDuff View Post
@eljefe, from your amazon.co.uk link, am I correct in assuming you are in the UK? If so, by my understanding, UK building regulations stipulate you must allow for both purge ventilation (which I believe your fan solution will provide for) and also background ventilation of at least 8000mm2 equivalent area. If you are in a basement, I think the rules are slightly different, depending on the specifics of the structure. All depends how much you're sticking to regs though.
Nope, just shopping on Amazon.co.uk
Old 26th May 2018
  #29
Lives for gear
Two issues to consider.
Mechanical isolation from the compressor
The air moving it's self.

For the air moving, the lower the velocity the better. (Larger ducts)

For the mechanical isolation, you want distance and flexible connection (Rubber ducts)
Old 26th May 2018
  #30
Gear Nut
 

Quote:
Originally Posted by eljefe View Post
So I have been researching the concept of HVAC and trying to figure out which system is best for a basement studio......
Maybe this is helpful: Building a Dead Vent for HVAC System - Soundproofing Company
Topic:
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