how can venting ever be soundproof?

[jrp]

Venting needs a direct tunnel from the inside of a room to the outside, right?
So in a soundprooved room, how can this be possible without noise using the tunnel to go outside?
i have no idea...

[Gdupproductions]

Originally Posted by jrp

Venting needs a direct tunnel from the inside of a room to the outside, right?
So in a soundprooved room, how can this be possible without noise using the tunnel to go outside?
i have no idea...

Soundproof ?.....no need for that.

[Rod Gervais]

Originally Posted by jrp

Venting needs a direct tunnel from the inside of a room to the outside, right?
So in a soundprooved room, how can this be possible without noise using the tunnel to go outside?
i have no idea...

The first thing you have to do here is to lose the idea of soundproofed rooms...... they don't exist (not on planet earth anyway)

There are just varying degrees of isolation - and the levels are different through the same assembly at differing frequencies...... much less at low frequencies than at higher frequencies.

Once you understand that - then it makes getting your head around the other a little easier.

Everything (that matters) is related to the degree of isolation you need at any particular frequency......


Isolation boxes - or commercially manufactured duct isolators - do a very good job of absorbing the sound as it passes through them - first and foremost.

There is also the fact that one of the tricks for DIY isolation boxes have a lot of corners the air has to turn to complete it's path - and each turn is equal to a longer distance of straight duct.

For example, for square and rectangular duct the following general rules of thumb apply (Best to worst cases in descending order).

1. Square elbow with "Turning Vanes" - EL 10 (The vanes are usually a
requirement in commercial work, and it's quite rare to find a residential
contractor who'll go to the expense).

2. True radius elbow - "Heel" and "Throat" are curved - EL 10 to 20,
depending on configuration

3. Radius elbow with mitered throat (a 90 degree inside corner) - EL 30 to 45

4. No elbow - EL 55 and up.

EL stands for the Equivalent Length in a straight duct run.

So you have a combination of absorption and resistance working in your favor. (In the very best of systems we also use active noise cancellation - but this is extremely expensive, and is usually only dealing with a very small frequency range (typically meant to help quiet the system noise itself))

Now let's couple this with a good design concept for split system fresh air handlers.......

Introduce the incoming air on the return air side of the air handler just before the point where the return air duct ties into to the unit.

Install the relief outlet on the return air side of the system at least 10' away form the fresh air inlet and install a barometric damper to create positive pressure within the room. (You need a relief outlet or you will not get fresh air once the room pressurizes.)

The majority of sound will travel the part of least resistance - which means it will be pulled from the space into the return air duct - and in turn travel back towards the space itself - with just a slight amount of air escaping the system heading towards the outside world.

If you have separate system for fresh air (let's suppose you're using a mini-split and thus need a dedicated system for fresh air) - in this case deal with isolation through the use of fully lined duct (if at all possible this is always the best case for quiet duct runs) - 3 or 4 90's and a iso-box on both the inlets and outlets (the same as you would with a split system)

Having your outlets exit the building higher rather than lower also helps.....

In the end - there is always going to be a small degree of loss in isolation - but with properly designed systems this loss is so miniscule as to be nothing worth worrying about.

I hope this helped,

Rod

[jrp]

thank you, yes of course this helped. Very detailed explenaition!
Still i must admit i am having trouble visualizing how this looks in reallity.
What about the pipe that the air travels through?
I suppose with double walls you want to use something flexible to keep the inner and outer structure as seperated as possible?
Then the insulation is done on the outside of the room within a room, right?

I did some more searching, I found these things, are they of any use in studio construction?
Telefonie-Schalldmpfer mit 125 mm Durchmesser, 43,00 €
Sonodec Schallgedmmt 127 mm lfm., 6,95 €

[wellnessmusic]

Originally Posted by jrp

thank you, yes of course this helped. Very detailed explenaition!
Still i must admit i am having trouble visualizing how this looks in reallity.
What about the pipe that the air travels through?
I suppose with double walls you want to use something flexible to keep the inner and outer structure as seperated as possible?
Then the insulation is done on the outside of the room within a room, right?

I did some more searching, I found these things, are they of any use in studio construction?
Telefonie-Schalldmpfer mit 125 mm Durchmesser, 43,00 €
Sonodec Schallgedmmt 127 mm lfm., 6,95 €

Hi There,
I think I understand your problem and Rod gave you a lot of helpful information. I just want to drop an idéa about a way to maintain the STC ratio / decoupling as much as possible as for ducting.
I made a draft (please see below) where you can find how it works. Two independent fibre-glass tubes with a small airgap in between (caulked with acoustic sealant). I haven´t tried this idéa yet but I think this will work even better comparing to flexible ducts with rockwool inside. Some of these flexi-ducts are perforated but also turn out to be too much rigid in a wall construction with a narrow airgap between the two walls. I think this idé would work well and of course you need silencer mounted tightly on both sides of the wall.
I also attached some pictures how I "decoupled" the electrical pipes in the wall in order to avoid the pipes bending an makes unescessary pressure against the rockwool.

Kindest regards / Bjorn

[wellnessmusic]

Forgot to post a picture of the rockwool-pipe:

[Rod Gervais]

Originally Posted by jrp

thank you, yes of course this helped. Very detailed explenaition!
Still i must admit i am having trouble visualizing how this looks in reallity.
What about the pipe that the air travels through?
I suppose with double walls you want to use something flexible to keep the inner and outer structure as seperated as possible?
Then the insulation is done on the outside of the room within a room, right?

I did some more searching, I found these things, are they of any use in studio construction?
Telefonie-Schalldmpfer mit 125 mm Durchmesser, 43,00 €
Sonodec Schallgedmmt 127 mm lfm., 6,95 €

I was unable to translate - so I really can't comment on the first - - but the flex duct is not a bad idea to make the final connection from a hard duct to an isolation box. Just make sure to keep the run very short - I often use this method to decouple (when using hard duct - if using fiberglass duct board this is not necessary) - but the connection is only about 1' in length.

I really do recommend an isolation box - it's a hard connection constructed on the outermost wall face - and it serves 2 purposes - the first being increased isolation at the penetrating point - the 2nd being that it is sized to reduce the velocity of the air flow.

The same volume at a lower velocity translates to a much quieter flow of air into the room.

Don't forget - air itself also creates noise as it moves - both through the duct and through the grille

Rod

[wellnessmusic]

Originally Posted by Rod Gervais

I was unable to translate - so I really can't comment on the first - - but the flex duct is not a bad idea to make the final connection from a hard duct to an isolation box. Just make sure to keep the run very short - I often use this method to decouple (when using hard duct - if using fiberglass duct board this is not necessary) - but the connection is only about 1' in length.

I really do recommend an isolation box - it's a hard connection constructed on the outermost wall face - and it serves 2 purposes - the first being increased isolation at the penetrating point - the 2nd being that it is sized to reduce the velocity of the air flow.

The same volume at a lower velocity translates to a much quieter flow of air into the room.

Don't forget - air itself also creates noise as it moves - both through the duct and through the grille

Rod

Hi Rod,
I totally agree. What do you think about my idea presented above? Often these flexible ducts turn out to be too much rigid when using short lengths. Another may be the lack of proper insulation. What do you think Rod?
Cheers! / Bjorn

[jrp]

thank you people! I was thinking of using the flexible duct all the way.
From the inside of the room through both walls directly into an isolation box.
In the box i can make as many angles as i wish and install the vent.
Guess i need a strong machine here, right?

Is oit a good idea to place the holes in the wall facing each other? Our wall has a 160mm gap.
How big should the diameter of the duct be? 100mm?