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Whats the professional way to bring down ventilation crosstalk between rooms?
Old 10th March 2014
  #1
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nickelironsteel's Avatar
 
🎧 5 years
Whats the professional way to bring down ventilation crosstalk between rooms?

Hi

Industrial silencers are not working below 1k
Ive heard about a labyrinth with rockwool

How is it done properly?
Old 10th March 2014
  #2
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Rod Gervais's Avatar
 
🎧 15 years
What "industrial silencers" are you referring to? There are a lot of industrial silencers that work well below 1K........

What is your particular need here?

Rod
Old 10th March 2014
  #3
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🎧 5 years
The usual method between typical rooms is lined 'U' or 'Z' transfer ducts but it all depends on how much sound reduction you are trying to achieve and how much static pressure drop can be accommodated (you want to stop the noise but not the airflow).
Old 10th March 2014
  #4
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nickelironsteel's Avatar
 
🎧 5 years
thanks so much for your reply

heres how it is: air comes into the control room then in series (sigh) goes to the amp and further into the vocal room
its a swiss product by TROX CA100 http://www.troxhesco.ch/xpool/downlo...lets/6_5_C.pdf

don’t thing "transfer ducts” (if you are referring to something like this:http://www.buildingscience.com/docum...lles-and-ducts)
will provide enough sound isolation.

are there any industrial (readily available) silencers that “work”?

anyone got experience with building rock wool labyrinths in series for the air to travel and how to propel it back up to speed?
Old 10th March 2014
  #5
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Rod Gervais's Avatar
 
🎧 15 years
OK - not what I would have used...... what I was referring to was something more along the idea of this:

Supplier of Preference for Air Distribution: Price-HVAC

I have used these products in the past (in commercial applications where "home built" was not an option) and was pretty amazed (the first time I used them) that with a unit that was only 4' in length - some one standing at one end (having a normal conversation) sounded like they were whispering when I was directly at the other end...

To begin - you do not want to propel anything back up to speed........... everything of importance is about large volume/low velocity.

If you want to move 100 cubic feet of air per minute you could do it in a 6"x6" duct, a 12"x12" duct or a 10'x10' duct - the exact same amount of air moves in either case - the only difference between the 3 examples has to do with velocity......

In the 6"x6" duct the air would be traveling at a rate of 400 fpm (feet per minute); in the 12x12 duct the velocity would be 100fpm; and in the 120"x120" duct 1fpm.

In all 3 cases volume would be exactly the same (100cfm)- however (assuming a straight run of duct - so no buffeting in any case - and open end ducts so as to not introduce noise from louvers) in the first case the air flow (at the point where air was exiting the duct) would be very noticeable - in the 2nd barely perceptible - and in the 3rd physically impossible to hear.

By the same token - as you increase the size of the duct prior to entering the space, with the duct being lined in either case (with otherwise identical absorbent materials) you increase the amount of attenuation the baffle can provide due to the increased surface area of those absorbent materials.

My basic rule of thumb (for studio design) is to provide systems so that the air general system flow never exceeds 300fpm (which is considered very quiet) and maintain levels at 100fpm or below at the points where the air actually enters the room.

U shaped baffles aren't all that great - but can provide decent isolation levels if the open ends do not point into the room(s) they are serving...... up helps a lot in that regard.

When I design box type baffles I generally try to design them so the inlet/outlet enter/exit the box on either the sides or top/bottom as opposed to the 2 ends if at all possible..... this to decrease the straight through effect....

I view 3 baffles between the inlet/outlet as being the minimum number from the perspective of sound isolation.........

Rod
Old 12th March 2014 | Show parent
  #6
Lives for gear
 
🎧 5 years
Quote:
Originally Posted by nickelironsteel ➡️
don’t thing "transfer ducts” (if you are referring to something like this:Info-604: Transfer Ducts and Grilles — Building Science Information)
will provide enough sound isolation.
I was actually referencing something like that shown here, Sound Attenuating Transfer Duct | Michael Schwob. That is what is commonly used in commercial construction but they may not provide sufficient attenuation for very high sound isolation constructions.

Quote:
Originally Posted by nickelironsteel ➡️
are there any industrial (readily available) silencers that “work”?
HVAC Attenuators | IAC Acoustics
Sound Attenuators | Commercial Duct Silencers for HVAC Systems

I have found these to work well, however you have to select them properly for each application. You also want to consider that the airflow though attenuators generates noise and you want to make sure that your airflow is slow enough that you don't end up with the attenuator adding to the noise levels.

Attenuators also represent some resistance to airflow which results in static pressure drop across the attenuators. Too much total static pressure drop and your HVAC system may not be able to move the air properly, if at all. That's usually more of a concern with commercial HVAC systems where you may have long duct runs, multiple turns and splits, terminal units, dampers and so on that all have some associated static pressure drop.
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