Sound modeling from AutoCAD 3D?

[VolvoHeretic]

I'm not too concerned with the R-value, but I'm confused with the sound absorbsion claim. If compressed 702 is good, shouldn't compressed batts be better than fluffy batts? I bet I could stuff 8" R-25 into a 2x4 wall.

I once was involved with building two giant 20'x12'x16' pipe organ enclosures for the biggest pipe organ between Minneapolis and Salt Lake City(so the paper said), which used swinging plywood louvers at the front to control the volume. They were just 2x6 walls with 5/8 drywall on both sides and without any insulation inbetween and I always wondered why not.

I love the way stereos sound outside and I play them outdoors whenever my neighbors are gone. I've wondered for years why inside, not so much.

So, there is no way through creative wall shapes to dampen the first, second, or third order modes with something relatively thin and I'll just have to lie with my head in the lower corner for good reception?

See? If I didn't ask the dumb questions, I wouldn't learn anything at all.

One more question; Am I right to assume that 90 degree corners are the worst for creating standing waves? Like bouncing balls off of a pool table? Which would be better than, less than 90 or greater than? If I turned the corners into two 45's would that help?

 

[RevMen]

I'm not too concerned with the R-value, but I'm confused with the sound absorbsion claim. If compressed 702 is good, shouldn't compressed batts be better than fluffy batts? I bet I could stuff 8" R-25 into a 2x4 wall.

I don't know the specifics, but 703 is made differently than normal batts. I think the fibers are spun shorter. It's not compressed, it's just made more densely using a different process.

Even if compressing a batt made it as absorptive as 703, it would still end up being thinner, meaning it would not be able to absorb lower frequencies as well. A wider airspace filled with normal density batt is what you want. The insulation's job isn't to block sound the way a wall does, its job is to absorb sound that's bouncing around inside the cavity.

So, there is no way through creative wall shapes to dampen the first, second, or third order modes with something relatively thin and I'll just have to lie with my head in the lower corner for good reception?

You absolutely can build membrane absorbers and place them on your walls. There's just no point in putting a thin airspace behind a layer of gyp that's behind another airspace.

If you're really itching to build a curved wall surface, your convex rare wall idea does have some merit. You might also want to build some on the side walls. I'm worried that you won't be able to get enough of a radius on curve to have a lot of effect on low frequencies, though.

One more question; Am I right to assume that 90 degree corners are the worst for creating standing waves? Like bouncing balls off of a pool table? Which would be better than, less than 90 or greater than? If I turned the corners into two 45's would that help?

When we work on band practice rooms or even large conference rooms, we often recommended angling at least on of the walls. The corner can be a problem, but parallel walls are an even bigger problem.

But that's really for spaces where there won't be any really meaningful absorption or wall diffusers. Since you have complete control over your room, I think you'll be better off just putting absorption and/or diffusion in the correct locations.

Unless you want to build a slanted wall. It absolutely wouldn't hurt you to do that. You don't need anything as extreme as 45 degree corners. Just flaying out a wall or two 8 degrees would be plenty to have the desired effect.

 

[VolvoHeretic]

If you're really itching to build a curved wall surface, your convex rare wall idea does have some merit. You might also want to build some on the side walls. I'm worried that you won't be able to get enough of a radius on curve to have a lot of effect on low frequencies, though.QUOTE]

That's why dream #3 will be smaller tighter arcs placed at the 1/2 and 1/4 modes (nodes?) on the three front and side walls with an arc at each corner (waves). I don't know what to do with the back wall.

 

[VolvoHeretic]

Wifey is walking around the house with her fingers stuck in her ears with my NEW sort of Altec A8 clones pounding upstairs. When I move them downstairs into my Mancave, how can I Isolate the basment from the upstairs? I will be stuffing the 2x10 floor joists with r-30 f.f. f.g insulation, but what next? Sound channel, durarock, then dry wall???

 

[RevMen]

What does your floor/ceiling system look like now? 2x10 joists... what's above? What's below?

What ductwork, if any, do you have in this space? Pictures would be very helpful.

Is it the bass that bothers her? Or all of the music?

 

[VolvoHeretic]

Yep, 2x10 joists @ 16" o.c. under 3/4" plywood sub floor. The living room carpet above the floor is getting ripped out for laminate flooring and there will not be any underlayment, just a thin layer of foam under the laminate. No duct work in that room other than (4) 6" heat runs to the registers that pass the entire width of the room. The stereo is still upstairs right now. The bottom of the joists are already low (7'-0"), so I can't see adding another layer of framing below them (my nephew is 6'-7" tall).

 

[RevMen]

The living room carpet above the floor is getting ripped out for laminate flooring and there will not be any underlayment, just a thin layer of foam under the laminate.

Yikes. You're going to hear a lot of foot traffic downstairs after that conversion, but if that's what you gotta do, that's what you gotta do.

I think best, reasonably priced, thing for you is to put 3" or more of batt insulation between the joists, hang resilient channel from the joists, and attach a layer of drywall to the RC. The 10" cavity depth and the RC will help reduce both footfall noise coming down and music noise going up. Be sure to install the RC and drywall correctly. You've got to make sure you don't short circuit the RC by putting any screws through the drywall into the joists.

 

[VolvoHeretic]

Thanks Revman, we walk around in stockings only and it's just two of use. So, no egg cartons?

 

[truevis]

For room/building modelling, also consider Spark from Autodesk http://labs.autodesk.com/utilities/spark/
It is pretty much a Revit Light which will run until July for free.

(Also suitable for people who used to own Volvos with B18 or B20 engines.)

 

[truevis]

...I have been looking for someone with a virtual windtunnel to import this thing and tell me if if will stick like glue at 250mph or flip over backwards. They are hard to find for free.

How about Project Falcon? "Model using wind direction/strength and resultant airflow/pressure."
http://labs.autodesk.com/utilities/falcon/
http://www.youtube.com/watch?v=UrrOA0rlaCg&hd=1

 

[Ice_Cubit]

...

 

[VolvoHeretic]

Thanks Truevis, just what I needed. I will have to stay up late tonight and do some reading.

 

[jeff0616]

I just finished building a community theatre and had to investigate acoustics. There are a couple of rules to begin with.
1. Never have flat walls facing each other. If you do, use carpeting or acoustic material on one of them.
2. You can tell if you have a problem by using a sound generator (test CD with good speakers). Place the speaker in different places in a quiet room. Crank up the test CD. Walk around. If you hear a warble, you have an unwanted reflection or resonance. Use acoustic material where needed or raise/lower the speaker(s).
3. Reflecting the sound to your seating area with a curved surface or multiple flat surfaces is generally good--test by noticing the volume/warbling.
4. If you want to get a first hand lesson, try the cathedrals of Europe. Some of them will add echos--up to five times. This is not a good effect for Jazz and many Genres, though.

Good Luck,

BTW neat ride,
jeff0616

 

[VolvoHeretic]

I've just figured out that I can convert my virtual car into a format that the AutoCAD Falcon wind tunnel program can import. Unfortunatly, that program only runs on 64 bit computers, but fortunatly, I will soon be getting a super-duper fast new computer at work which should do nicely. Happy Days. I will report back when all of that happens.

 

[VolvoHeretic]

How about Project Falcon? "Model using wind direction/strength and resultant airflow/pressure."
http://labs.autodesk.com/utilities/falcon/
http://www.youtube.com/watch?v=UrrOA0rlaCg&hd=1
View attachment 321924

http://www.youtube.com/watch?v=AKn-LTNa4rc

Truevis, since this is my thread, I can go off topic, I hope. I was never passed ever in the mountains, and once while living in southern California, 1986, while desending Mt Palermo, I passed Road and Track Magazine driving up the mountain with a bunch of cars, which included a Porsche 928, C4 Corvette, and Ferrari 328 among others. I did a broadie(?), caught up to them and passed a few before they pulled over for a photo session. We talked for a while, they took pictures of my car which they never published, and went on their way. I could have kicked all of their asses since I had a 1000 pound weight advantage.

PS; I invented the Fast and the Furious, but just did a lousy job.

 

[VolvoHeretic]

Just got the basement useable finally, but with no sound treatments or insulation of any kind. Standing downstairs with a pair of Altecs blasting away upstairs, it didn't sound too bad below, mostly muffled with no rattles.

I put the pair of EV sentry IVs down stairs and a totally different story. Uptairs it is god-awful, the two in floor 6" heat ducts were transmitting sound threw the registers sounding like someone was hitting them with a drum stick. Everything, the bookcase, pictures, walls... were rattling! Not sure how I am going to fix this so I can hang out in the basement mancave with anybody else in the house. Next time I am alone, I will take sound pressure readings.

 

[RevMen]

the two in floor 6" heat ducts were transmitting sound threw the registers sounding like someone was hitting them with a drum stick. Everything, the bookcase, pictures, walls... were rattling! Not sure how I am going to fix this so I can hang out in the basement mancave with anybody else in the house.

I think you've got 2 different problems.

Can you access/replace the 6" ducts with acoustically lined flex-duct? That'll reduce the highs and upper mids going through your heating system.

I think it sounds like everything is coming through the ducts because the high frequency stuff is causing you to localize the registers at sources. Low frequency stuff can get through floors and walls pretty easy and takes a pretty good effort to solve. If you don't have a ceiling in your downstairs area yet see my earlier suggestions about what to do there.

 

[VolvoHeretic]

RevMen, the ceiling has a plastic track and wood fiber panel drop ceiling that's stapled directly to the floor joists and installed from one end to the other with the tiles as you progress. I will be taking that down and can change out the duct or maybe wrap them with duct insulation. I suppose flex would have a better disconnect.

I need to figure out how to make the drywall covering removable from the sound channel.

 

[danbisawsum]

Solidworks is the obvious answer here guys

 

[VolvoHeretic]

Finally, don't these women ever go shopping? Got to crank up the stereos and 100 db upstairs shows up as 70 db downstairs, and 100 db downstairs is 76 db upstairs. The rattle wound up being the heat registers. Putting my full weight on them didn't help so I doubt if just screwing them to the floor will remedy the rattle, but removing them did. I will remove the dampener on them and see if that fixes the problem since there is no reason for them to remain.

RevMan, what kind of heat duct are you referring to? I only know of un-insulated flex hose. I have no idea if pipe insulation would fit over heating metal duct. And overstuffing the floor joists with fiberglass insulation is a bad idea? If I remove the drop ceiling, whatever I replace it with will have to be removable. I am thinking of sound channel spaced 4 feet on center, 1/2 inch sound board, and then 1/4 inch 4x8 oak plywood with batten strips over the screws and joints.

How about 1/2 inch Durarock underlayment on top of the 3/4 inch plywood sub-floor above the floor joists? Then 1/8" foam under-layment, and then the laminate flooring?