Starting Fresh and Obeying the Laws of Physics

edenorchestra · Post by **edenorchestra** » Thu Dec 02, 2004 3:50 pm

pheww . . you guys are on top of it . . . Sounds like the whole HVAC needs revamped . . good . . better now than later . . right now the plan is to have an open room . . but then again maybe not . . oh my so confused . .

Lets do this . . I have a big open room right now . . if I were to decide to eventually make a separate control room I WOULD be best to make provisions . . I am more than open for a total redesign on the duct work, my guitar player works for a sheet metal fab shop that specializes in insulated ductwork . . but they may have never done a studio, it was their plan that I submitted here . . fresh start?

Regards,

AVare · Post by **AVare** » Thu Dec 02, 2004 4:48 pm

edenorchestra wrote:pheww . . you guys are on top of it . . . Sounds like the whole HVAC needs revamped . . good . . better now than later . .

Hardly a revamp, refining, yes. Like you wrote, better now. Better than turning on the HVAC the first time and having major noise problems.

A thing to note (I new I forgot something

) the HVAC system, including the ducts should mechanically isolated from the inner room. Not as big a deal as it sounds, suspend the ducts from the outer wall. I am using "wall" in the sense of partition. A ceiling is a wall lyng down.

Any thoughts on venting for the bathroom?

right now the plan is to have an open room . . but then again maybe not . . oh my so confused . .

Part of why design is 90%

Lets do this . . I have a big open room right now . . if I were to decide to eventually make a separate control room I WOULD be best to make provisions . . I am more than open for a total redesign on the duct work, my guitar player works for a sheet metal fab shop that specializes in insulated ductwork . . but they may have never done a studio, it was their plan that I submitted here . . fresh start?

From I have seen, there is no need for a fresh start. The start is good. Good studio design is working from concept to completion with attention to many more details than a regular building because the concepts are not relatively widely known in the construction industry, and tolerances are much stricter.

Give some thought to what you would like in a control room so that a rough area in the room can be designed for that possibility.

A quick note to give confidence in what has been presented so far. the overall duct size to grille is fine. Refinement on the grilles, and that part is done. The main duct needs to increased in size. One major change. I didn't study the return ducts, but the same criteria (500 cfm) applies.

Working on the start, have you thought about a noise study around the buiding so we can determine if a floating floor is necesary for isolation from the outside? From what I gather the question is the train tracks.

Looking good;
Andre

edenorchestra · Post by **edenorchestra** » Fri Dec 03, 2004 5:29 am

A thing to note (I new I forgot something ) the HVAC system, including the ducts should mechanically isolated from the inner room. Not as big a deal as it sounds, suspend the ducts from the outer wall. I am using "wall" in the sense of partition. A ceiling is a wall lyng down.

I understand this, my plan was to have those ducts above the outer wall in the attic space, still need to understand how they come through the outer through the air space and throuh the inner wall however.

The bathroom is partitioned and will have the HVAC equipment in the same room (mechanical/pee room).

I will give great consideration to the control area in the next few days.

Working on the start, have you thought about a noise study around the buiding so we can determine if a floating floor is necesary for isolation from the outside? From what I gather the question is the train tracks.

Super good idea, where do I begin, the best thing I have is the el cheapo Radio shack db meter that doesn't go below 50db and god only knows what the curve looks like on the frequency response . . probably a roller coaster . . .

your consistent advice is most appreciated . .

AVare · Post by **AVare** » Fri Dec 03, 2004 7:47 pm

I understand this, my plan was to have those ducts above the outer wall in the attic space, still need to understand how they come through the outer through the air space and throuh the inner wall however.

Good on the first point. The second is relatively straightforward, in my mind at least. The attached drawing should help.

Nothing is firm in the drawing, it is to give the idea so you can develop the best, including cost, design. A consideration is reduce the number of ducts but increase their size. Check the costs with your friend.

The bathroom is partitioned and will have the HVAC equipment in the same room (mechanical/pee room).

Good to read that. We will have address mechanical isolation for the HVAC equipment. Otherwise it could end turning the entire building into a drum skin for the vibrations.

I'll address the noise survey issue when I am more awake. It will require some creative thinking of what is needed, you have and how we achieve it. Sort of like McGyver of Acoustics.

Andre

knightfly · Post by **knightfly** » Sun Dec 05, 2004 5:05 am

Andre, appreciate the "sleep-posting" syndrome as I'm quite familiar with it - but, where's the outer leaf in your drawing, and how are you decoupling the flanking path (created by a through-duct) between inner and outer leaf? Steve

AVare · Post by **AVare** » Sun Dec 05, 2004 2:49 pm

I haven't forgotten about the noise survey, just haven't figured it out enough yet to post something useful.

knightfly wrote:Andre, appreciate the "sleep-posting" syndrome as I'm quite familiar with it - but, where's the outer leaf in your drawing, and how are you decoupling the flanking path (created by a through-duct) between inner and outer leaf? Steve

I'm not clear on your questions so forgive the vagueness in the questions.

What outer leaf (that isn't there, talk about a confusing sentence) are you referring to? Think of the breakout as being lined duct for outside (in this case to the cavity) ventilation.

Flanking path as in something like in the drawing attached? The absorbent material lining the duct.

There is no doubt that I have missed something. Unfortunately even with your questions I can't see it.

Thanks Steve! As I wrote the above paragraph, I realized something that I DID miss. The duct has to be decoupled from the ceiling to avoid HVAC
machine noise being physically transmitted to the ceiling. I will include that revision in the drawing.

Andre

edenorchestra · Post by **edenorchestra** » Mon Dec 06, 2004 9:08 am

I too do not see both leaves in the ceiling. The plan is outer leaf on the chords of the existing trusses with the duct work above that. Then resting on an entirely new wall are joists with the second (inner) leaf. So the duct work is in the largest opening in the truss, that is for the supply

Right now I am making a scale model of the building, both to help explain things better and to get my creative juices flowing a bit more . . this will take some time . . but I think it will be worth the effort . . besides that . . its good fun.

I bumped the trusses so they're not quite lined up . .

Regards,

AVare · Post by **AVare** » Mon Dec 06, 2004 3:51 pm

Nice rendering!

I hope this helps. It is based on Edenorchestra's drawing of the proposed HVAC system. This second leaf thing has me confused as much as two of you.

Perplexed;
Andre

[edit] (04-12-07) Read the thread and noticed that my drawing was not attached. Attempted to attach it so that the post makes sense,

AVare · Post by **AVare** » Tue Dec 07, 2004 3:40 pm

I have been giving the noise survey a lot of thought. It is critical because if outside noise is not adequately contained, the weakest point in the sound isolation will make the rest of the work meaningless. If the noise is not a problem then going with a floating floor will be a massive waste of time and money. Paul wrote somewhere recently that the floating floor in his studio is 40% of the construction cost. The noise question, as I understand it, is train tracks about 500' distant. Other sounds, and neighbours are not an issue.

Working from what we have spoken about, my first thing was to check that the wall construction is adequate. I modeled a wall with:

1/2" gypsum board, 2 layers
2x4 studs
5" airspace
insulation in airspace
2x4 studs
1/2" gypsum board, 2 layers

in Insul. The results are shown in the attached JPG. For those reading this who can't see the graphic, the STC is 67 with the TL 30 dB@50 Hz. The wall system will not be a problem with isolating airborne sound from the outside. This confirms our concern being if a floating floor is needed.

What we need for the sound survey is at one level fairly simple.

1) microphone with good low frequency response
2) a way of calibrating the microphone
3) electronics to accurately record the microphone output
3) system to analysis the the recording from 3).

Where it starts to get difficult is 1) and 3) need low enough noise figures that the self noise does not mask the desired signal. It can be quite expensive to achieve this. That is why the Radio Shack SLM only goes down to 50 dB SPL.

Good low frequency response is primarily with omni microphones. Do you have any good omni mics or friends with that you can borrow?

Assuming that you do, hook the test mic to your recording system with a calibrated level control,

With the test microphone and RS meter side by side outside, record a pink noise source with the RS meter indicating 55 dBC. Note the recording channel settings.

Take the test mic to the quietest place you can think of. Put the mic in a heavy walled sound absorbent lined box ( do like that fancy phrase for a road case?) with the just enough open to run the cable.

Record again and increase the gain until the level equals what you got from the calibration to the RS meter. This will hopefully give an indication of the self noise level of the mic/electronics.

Put that data through software with at least 1/3 octave or preferably FFT analysis capability.

Calculate the self noise spectrum.

Post/email (hopefully both) the results for review. We will be looking at the overall level and the spectrum to determine the masking.

Assuming the above is acceptable, find out when a train is going by and record noting the recording levels sos that we have a calibrated reference to the RS meter.

We can then Analise the results.

The RS calibration is not great, within 2 dB, but for our work we can take that into account.

Another option, and one that would remove any problems with technique band-aid systems would be to rent a suitable meter. Bruel and Kjaer would have setups for that. I do not know the prices of the rental unfortunately. Something like their 2260 Investigator with software.

edenorchestra · Post by **edenorchestra** » Tue Dec 07, 2004 10:43 pm

Thanks Andre . . that's quite a chore . . I will need some time for that. I have to go out of town on business for a few days and then dig out some equipment to run the tests. I will print out your memo which is most helpful.

BTW the "rendering" is actually a real model made out of balsa wood that I took a photo of . . everyone that sees it thinks I 3D rendered it on a computer . .

cheers . .

AVare · Post by **AVare** » Fri Dec 10, 2004 4:40 am

Maybe it dodn't catch, but I added the drawing that should have ben there on my post, three messages ago.

Does this clear up the second leaf question?

Andre

edenorchestra · Post by **edenorchestra** » Fri Dec 10, 2004 2:23 pm

I am not totally clear still on the second leaf in the ceiling but I think I have a solution coupling the duct touching the inner leaf to the outer leaf with a rubber duct decoupler . .

Here is what I have been doing on the control room as I am more thinking that the open control room could be more of a hassle than its worth.

Notice the bathroom-mechanical room, is it ok to do it like this?

Regards,

edenorchestra · Post by **edenorchestra** » Fri Dec 10, 2004 2:31 pm

Bump . .

Here is the ACAD to date.

Edit - deleted incorrect file to avoid confusion, see below - steve

knightfly · Post by **knightfly** » Sat Dec 11, 2004 1:00 am

Not sure if it's just me, but I get a 0 kB file size and nothing when I download the zip file... Steve

edenorchestra · Post by **edenorchestra** » Sat Dec 11, 2004 5:38 am

Yes you are correct. .. I must have zipped it when the file was still open in ACAD . . .

try again . ..