Sono Flex Duct: Snake Oil or the Real Deal?

[gullfo]

so the silencers that i saw were "straight through" which implies the absorption panels in the flow and around the shell to provide absorption. i have no other details on their internals. i do know the ducts where about 1m in diameter in the big room, perhaps larger. the secret to all of this was constantly increasing the overall sizes to reduce the flow rate. there was no double penetration (as far as i can tell) as the rooms in Galaxy are all large concrete shells within the overall building shell. the main room weighs in at about 300 tons.

as far as a normal set of construction, there are several options: baffle boxes on each side of the mass with a flexible duct encased in mass-equiv sleeves (only really use this in loud situations), ducting which has absorption and can be passed off the main branch into each room (i like duct board for this most times) which minimal contortions, or flex duct (which i use in small places where i don't care much about the inefficiencies from drag). but always leverage the plenums in room.

[psb_87]

Source of the post so the silencers that i saw were "straight through" which implies the absorption panels in the flow and around the shell to provide absorption. i have no other details on their internals. i do know the ducts where about 1m in diameter in the big room, perhaps larger. the secret to all of this was constantly increasing the overall sizes to reduce the flow rate. there was no double penetration (as far as i can tell) as the rooms in Galaxy are all large concrete shells within the overall building shell. the main room weighs in at about 300 tons.

as far as a normal set of construction, there are several options: baffle boxes on each side of the mass with a flexible duct encased in mass-equiv sleeves (only really use this in loud situations), ducting which has absorption and can be passed off the main branch into each room (i like duct board for this most times) which minimal contortions, or flex duct (which i use in small places where i don't care much about the inefficiencies from drag). but always leverage the plenums in room.

Thanks Glenn,

What I have seen is simply flex duct by itself (connected to either a filter, fan, air handler or a HRV/ERV), going through the isolation shell, no baffle boxes, it either enters at an area with deep absorption (but sometimes not) or into a machine room for example, and then vented out from there into the control room/live room. In the case of Northward, the ducts are buried in deep fibre with "sideless" boxes which act as a buffer to decrease air friction noise as it comes out.

I'm finding it hard to picture the "silencers" used in Galaxy... from your description I am just imagining the corridors around the control rooms/live rooms as being the silencers.

[bert stoltenborg]

https://www.decinternational.com/specif ... dec_25.pdf

[psb_87]

Source of the post https://www.decinternational.com/specif ... dec_25.pdf

Thanks Bert. The only part I am struggling to understand in all of this is how airborne sound from the control room or live room doesn't just go straight through the jacket of the flex duct?

Yes, I know you could use a baffle, or a straight through silencer etc, but I am talking about cases where nothing is used, apart from the fibrous treatment in the room itself surrounding the duct.

[bert stoltenborg]

Source of the post

Source of the post https://www.decinternational.com/specif ... dec_25.pdf

Thanks Bert. The only part I am struggling to understand in all of this is how airborne sound from the control room or live room doesn't just go straight through the jacket of the flex duct?

Yes, I know you could use a baffle, or a straight through silencer etc, but I am talking about cases where nothing is used, apart from the fibrous treatment in the room itself surrounding the duct.

You have of course to put something around it.
You can also make a straigth damped pipe or something. But when the flex duct is f.e. in the gap between two rooms you can realize these reduction numbers without screwing around with labyrint boxes or other fetishes.

[gullfo]

interesting thoughts - you need attenuation of machine noise (preferably before-or-as it exits the utility closet) and you need to reduce flow velocity, avoid duct induced noises, attenuate noises external to the duct (hence the "put something around it") and then once you penetrate the space, a means of further noise attenuation, preferably flow reduction, and distribution (in the CR, symmetrical since you'll have some noises and flows which are best balanced), and in the live room(s), preferably enough flow to keep the rooms comfortable and low noise (e.g. air flow over microphones).

HOW you do this, depends on the possible issues found in the design constraints.

Paul - Eric specifically pointed out the silencers since he found it humorous that many people built small units which did nothing to ensure low flow velocity or created noises due to turbulence. the scale of the units is quite impressive. and yes, the walkways around the rooms, and under them, and over them, all contribute to isolation for sure. but cutting holes through walls and ceiling (and floors) require thought about what is happening outside those rooms, or how multiple layer penetrations will be handled. not all studios can have 10'-30' separations between rooms and exterior walls

[psb_87]

You have of course to put something around it.
You can also make a straigth damped pipe or something. But when the flex duct is f.e. in the gap between two rooms you can realize these reduction numbers without screwing around with labyrint boxes or other fetishes.

This actually made me spit out my coffee

f.e. = fully enclosed?

[gullfo]

or you can use nested duct board sleeves to wrap it. some protection is afforded as well as some vibration reduction from loose duct flapping...