HVAC Transfer Baffle Design

I've been working on a redisgn for this studio and was just given a designed HVAC solution. I wanted to post the design to see if anyone has done this type of transfer baffle before. The gentleman says it will only have 20 db of noise in the room. That seems stupid quiet! I'm a little worried about certain aspects of the design. A little background: This is for a place that does VO exclusively. We do remote sessions via ISDN (so retro cool, I love it), phone patches and the like. a majority of the sessions have an engineer, Producer, checker, a sometimes a client as well. The space we have is a small 720 square basement with very low concrete ceilings. This has made the HVAC a nightmare to figure out. My floorplan has two control rooms that can each have all of the above members. Shared Vocal booth, with a machine room in the middle to contain all the noisy computers, and other audio equipment. This way, expensive gear like the ISDN Zephr and DV decks can be shared easily. I want to be able to do a remote session in one room, while doing a local session in the other, or sweetening or whatever. The HVAC guys are running all ducks lined on the inside, and insulated on the outside. So, any comments or advice from Ya'll? BTW, great forum here. Long time lurker, first time poster!

Here's the PDF trimmed on the edges...

I don't know if I necessarily buy the 20db claim, but the zigzaggy baffle idea is very similar to a homegrown silencer concept that I'll be building in my space. My goal isn't to have quiet ventilation, but rather, to have little noise escaping the room. --Keith :mrgreen:

Hi I have no answers for you, as I'm not in any way proficient with HVAC stuff... I do however have a few questions: 1.) Are you using METAL ductwork that is lined, or is the stuff like the Johns Manville SuperDuct (or Owen-Corning equivalent)? If it IS metal, wouldn't avoiding metal be better for sound reasons? 2.) Is the sound you are trying to prevent transmitting between rooms, or is it from the HVAC system itself (and that of the flowing air)? If it's from the HVAC equipment and air movement, I had heard that the turns should have 'sweeps', as this would cut down on turbulence -- although I don't know if this is a compromise to preventing noise within one room going to the next room (it would seem to me that for preventing noise from room to room, the more the abrupt turns and baffles, the better the reduction). 3.) If more baffle structures and turns are included, does this not restrict the movement of air? I'm sure that since you have HVAC pros working on this that they have taken this into account, and sized the ducts and equipment correspondingly.... 4.) The last thing I can think of is about where the ducts will be in relation to the walls... If you have double-wall construction, and the ducts are between the walls, isn't their proximity very important in order to minimize any 'third-leaf' effects? It's possible that some sound could go through the wall and bypass much of the duct length... thus it seems that this is maybe one area where one would want 3 or more leaves (as, in fact, it can't be purely 1, 2, or 3-leaved, because some areas will have different amounts of leaves at different cross-sections -- so the absolute rule CAN'T apply)... I say this because I'm dealing with a similar situation -- except that duct that I'm worrying about is the one above the inner-ceiling that feeds a room outside of the studio... You've probably taken this all into account, but I'm not sure I can see that from your post, or from the pdf diagram... Anyway, it sounds like a really cool setup, with the 'remote' stuff... K

1) Metal, lined on the inside and wrapped on the outside. 2) Both. Fortunately we only VO and we filter the serious low end out at the Mic. Makes the whole thing easier. 3) On the turbulence, he did talk about that at earlier meeting, but with these oversized ducts he said the velocity is low. 4) this was the toughest part. The ducts are so thin and are run around the walls from the low ceiling. They will be attached to the concrete, and suspended away from the double walls. I forgot to mention, the Machine room will have its own AC Split Ductless with the unit outside.

Luftweg wrote:

Hi I have no answers for you, as I'm not in any way proficient with HVAC stuff... I do however have a few questions: 1.) Are you using METAL ductwork that is lined, or is the stuff like the Johns Manville SuperDuct (or Owen-Corning equivalent)? If it IS metal, wouldn't avoiding metal be better for sound reasons? 2.) Is the sound you are trying to prevent transmitting between rooms, or is it from the HVAC system itself (and that of the flowing air)? If it's from the HVAC equipment and air movement, I had heard that the turns should have 'sweeps', as this would cut down on turbulence -- although I don't know if this is a compromise to preventing noise within one room going to the next room (it would seem to me that for preventing noise from room to room, the more the abrupt turns and baffles, the better the reduction). 3.) If more baffle structures and turns are included, does this not restrict the movement of air? I'm sure that since you have HVAC pros working on this that they have taken this into account, and sized the ducts and equipment correspondingly.... 4.) The last thing I can think of is about where the ducts will be in relation to the walls... If you have double-wall construction, and the ducts are between the walls, isn't their proximity very important in order to minimize any 'third-leaf' effects? It's possible that some sound could go through the wall and bypass much of the duct length... thus it seems that this is maybe one area where one would want 3 or more leaves (as, in fact, it can't be purely 1, 2, or 3-leaved, because some areas will have different amounts of leaves at different cross-sections -- so the absolute rule CAN'T apply)... I say this because I'm dealing with a similar situation -- except that duct that I'm worrying about is the one above the inner-ceiling that feeds a room outside of the studio... You've probably taken this all into account, but I'm not sure I can see that from your post, or from the pdf diagram... Anyway, it sounds like a really cool setup, with the 'remote' stuff... K