Sound modeling from AutoCAD 3D?

I may be slightly underselling Sketchup, but on the same token I think you're downplaying the realities of engineering analysis.
I understand where you're coming from, but I think you're overemphasizing the similarity between outright building design and tuning of a room. The tolerances for this process are on the order of several inches. Also, I think we have different understandings of the problem statement.

This is the original request:
If so, can you highly trained sound engineers calculate where I should sit to avoid all of the nodes and voids and where to place my speakers and how to set my EQ?
While you may have taken that to mean "can someone plug my AutoCAD model into acoustic modeling software," I took it to mean "can someone use the information in this model to do calculation that will help my room."

This is why I suggested modeling his room in Sketchup, because a Sketchup model would transmit the same information to us in a format that would be useful to any of us, not just those of us with AutoCAD. I'm not suggesting that he re-model his room, btw. In his first post he said that he could model it in AutoCAD, not that he had.

The motivation for touting the use of Sketchup for us in this forum to communicate our rooms to one another comes from experience. I do acoustical engineering analysis on a daily basis and I've found Sketchup to be more useful than AutoCAD for many tasks. Of course we have AutoCAD at our firm, but I actually don't use it very often (only to read client drawings).

When we make recommendations for acoustical treatment or mitigation, the important parts of what we're telling a client, what to do and why to do it, can easily get lost in an AutoCAD drawing. In Sketchup I can de-emphasize absolute dimensions and emphasize the principals at work. I don't actually send Sketchup models to clients, but I sometimes take snapshots from inside a model to insert as figures into a report, and they usually do a great job of getting the point across.

I'm really not the first to think of this use for Sketchup, not by a long shot. If you want an example of how Sketchup can be useful for a forum like ours, spend a little time checking out the models people have built at the John Sayers forum. They've been using it for years there to help one another do great acoustics.
 
...Also, I think we have different understandings of the problem statement.

...


I agree that this is the root of our disagreement.

I also agree that Sketchup can be used to aid in visualization, but I see that as being an extremely primitive form of acoustical analysis.

So, if the OP walked into your firm, how would you use Sketchup to dissuade him from the curved back wall idea? Or better yet, how could HE use Sketchup to determine the viability (or lack thereof) of his curved wall idea? He already knows how to use AutoCAD, so the learning curve point is moot.


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So, if the OP walked into your firm, how would you use Sketchup to dissuade him from the curved back wall idea?
Again, I'm talking about using Sketchup (and AutoCAD) for visualization and transmittal of dimensions. Not for analysis.

But to answer your question, I would use Sketchup, AutoCAD, or a sheet of paper in the same way to dissuade him from using a curved back wall. It's not a very complicated concept, so it really doesn't require software to communicate it. I would draw lines showing how an inwardly curved back wall would focus reflections to the center of the room, thereby allowing both speakers to "exist" on both sides of the room simultaneously, wrecking the stereo image.

Or better yet, how could HE use Sketchup to determine the viability (or lack thereof) of his curved wall idea? He already knows how to use AutoCAD, so the learning curve point is moot.
If he's interested in working on the problem by himself, then he should use whatever tool is most comfortable for him. Just like with mirrors, the angle of incidence is the same as the angle of reflection. Solving this problem in particular doesn't require any acoustical analysis software, just the ability to draw rays at specific angles.

but I see that as being an extremely primitive form of acoustical analysis.

You keep referring to some kind of acoustical analysis tool. What is it that you're talking about?

The most important room acoustics programs I know of are CATT, ODEON, and EASE. Is it one of these? There are some other packages out there that aren't as popular, as well. I haven't used CATT, but I have used both EASE and ODEON.

All 3 of them can work with Sketchup models, by the way. And a lot of people prefer Sketchup to any other interface for modeling a room. Like I said before, Skeptchup's level of detail is very consistent with the level of detail needed to do acoustical analysis.

ODEON:
We have made a plug-in for Google SketchUp (SU) that allow you to make direct use of SU models in ODEON. SU is a fun 3D modeling software which is operated very intuitively.

CATT:
SU²CATT is a SketchUp extension to export SketchUp models to CATT-Acoustic files. It exports models generated within Sketchup to the native .geo-format of CATT-Acoustic, including export of layers into several .geo-files and separate file with absorption material definition (ABS-directive in CATT).

If you've made your acoustic models within CATT before, this will save you tons of time. We actually developed the interface for in-house use first, and later decided that other people might benefit from it too.

"The use of SketchUp allows the user to create a building model for simulation VERY quickly and intuitively. It allows the software people to focus on the thing they are good at (Energy / Daylight / Acoustic modelling ) rather than on visualisation and geometrical modelling. It brings closer my personal Nirvana: Skecth design using full simulation tools, rather than cut-down 'simplifications'. What is most important to me, after many years of working with various geometry exporters based on the autodesk 3ds or dxf formats, is that in the experiments I have done with Daysim and CATT, the models exported from SketchUp are much less complex. Fewer polygons. Less calculation time. Less need for this type of geometry simplification."

EASE:
SU²EASE is a plugin for the 3D Software Google Sketchup to export Acoustic 3D-Models for use in EASE or Bose Modeler...
Main Features include:
-exports to .xfc format for use in EASE or Modeler
-Materials can be assigned within Sketchup
-Supports EASE standard material libraries
-integrated error recognition for common modelling errors

EASE:
EASE has the ability to import and export AutoCad and Sketchup DXF files

In finding those sources, I came across some other software packages I didn't know about or had heard of but never looked at.

Axys DDA:
Models can be imported into DDA from Odeon® , CATT Acoustic® and EASE® acoustic modelling software packages. Third party plug-ins are also available to import Google SketchUp® drawings into DDA.


L-Acoustics Soundvision:
SU4AC is a Google SketchUp plug-in written by Greg Longtin of Champion Enterprises. It is designed to help one quickly work with DXF, DWG and 3DS models imported from CAD software or acoustic simulation packages such as CATT, EASE and ODEON where one needs to reduce the model to what is required for electro-acoustic prediction. The sound designer can export and import models to/from SOUNDVISION.
Also note that this example is a Sketchup plugin that can act as a wheel-house between different acoustical packages.


And hey, look what I found: http://forums.sketchucation.com/viewtopic.php?f=323&t=27212&sid=8d079af64cec529edadf6b4ba80cf1bc. Sketchup plugin for acoustic ray-trace. I don't know how well it works but maybe it's useful for us.
 
Ok, I don't want to beat a dead horse here, as it's obvious we are talking about two different things, but what I see above is this: You've listed a bunch of programs that WILL perform the task at hand (acoustic analysis), and illustrated the fact that they are all compatible with Sketchup in some capacity. You've proposed the idea that someone trained in acoustics could use Sketchup alone to perform basic raytracing, but that the same person could also use a pencil and a sheet of paper to the same end... Which pretty much echos what I've been trying to say in the last several posts: Sketchup is not the right tool for performing any kind of acoustical analysis, even if the analysis required is so basic as to solely require simple raytracing. (Because even then, someone like yourself would have to provide the knowledge to do the raytracing properly and to then draw intelligent conclusions from the resulting data.)

I still don't see how it will help a guy trying to figure out the effects of a curved back wall on overall sound or where to place his chair to avoid standing waves...

Maybe the OP can chime in here to clarify the original question. Specifically, what he meant by "sound modeling".
 
I still don't see how it will help a guy trying to figure out the effects of a curved back wall on overall sound or where to place his chair to avoid standing waves...
His original question was about room modes. Room modes are pretty easy to solve because they're just based on the room's dimensions. To answer the question he's asking, we really only need to know the distances between opposing corners and flat surfaces.

Both AutoCAD and Sketchup models of his room would be helpful, because both would enable us to quickly extract distances between meaningful locations with a few clicks of the mouse.

This is why I suggested he consider creating a Sketchup model instead, as it would be a quick and convenient way for him to transmit all of the room's dimensions in one model that anyone here could download and observe, not just those of us with access to AutoCAD.

His second question, later in the thread, was about having a concave surface. It's a great question to ask on a forum like this, because I'm sure there are at least half a dozen people here who would instantly know not to do that. Problem solved.

It does not require any software to determine that a concave curved surface in a critical listening room is a bad idea. We don't even need room dimensions. Running a ray-trace on a room with a curved wall would reveal to us the location of the focal point, which I guess could be interesting, but it's not useful information in terms of answering the question. Knowing that there will be a focal point is all that's important.

Sketchup is not the right tool for performing any kind of acoustical analysis
No one is saying he should use Sketchup to perform an acoustical analysis, or that anyone here should use Sketchup to perform an acoustical analysis. I talked about the possibility of good scripts that allow us to do some ray traces in Skeptchup, but not once did I say Mr. Heretic should perform an acoustical analysis with Sketchup software (or software of any kind).

What I have been saying, over and over and over, is that Sketchup is a great tool for creating a model that can be transmitted to anyone. Such a model can inform someone of room dimensions for doing a hand calculation, or it can be imported into all of the major room acoustics software packages.

And that is the is the original intent of this thread.
I can 3D model my entire house in AutoCAD down to the nearest 1/8". If so, can you highly trained sound engineers calculate where I should sit to avoid all of the nodes and voids and where to place my speakers and how to set my EQ? :)
The OP was not talking about doing the analysis himself. He was talking about whether a model of his room that he built in AutoCAD could be used by someone to analyze his room. The answer to that question is yes.

It is also true that a Sketchup model could be used for the exact same task and, in fact, would be more useful, because it could be transmitted to anyone on the forum who was interested in taking a look.

You're on the right track, but you'll need to find someone with some sound analysis software, preferably someone who really knows how to use it, and find out what they need from you in terms of a file format. If there's a way for them to import a model, chances are good that AutoCAD can export the right format.
Your interpretation of his question was whether an AutoCAD drawing would be suitable for importing into an acoustical analysis package. You suggested he find out what file format to use. One of the best answers to that question is "Sketchup." Another good answer is "a .dxf export from AutoCAD."
 
Thanks guys. When I first posted, I didn't have a model, but it only took 15 minutes to create and twice that long to upload to the server and post. I was hoping you guys used software that could show all of the sound anomalies similar to that Olive Tree Terrain, but it's just like CFD analysis, everything you find on the internet is stuff for sale, but no one to providing the services, but I haven’t actually looked either.

I will just continue to try and visualize sound without a clue, my best luck so far is to thing of the 2D waves splashing around in a crowded pool and how the waves in the corners build up and splash out.

How about convex walls then?

roomdiagram-Convexwalls.jpg
 
Ugh. How about this: We stop bickering over this stupid software issue and you answer the guy's intensely simple question that apparently only requires room dimensions and a calculator. Ok?
 
... was hoping you guys used software that could show all of the sound anomalies similar to that Olive Tree Terrain, ...


Sorry man, I'm going to stop clogging your thread with BS and maybe someone will hook you up with a quick and dirty analysis.
 
How about convex walls then?
Much better than concave, but really not necessary. It would take up space that you don't have to sacrifice.

So can you give us the basic dimensions of your room and the existing surfaces? I can see from the picture you've posted that it's long and skinny but that's about all I can tell.
 
It's not that long. I just measured it and will post it up when I get a chance. I will also recheck Sketchup and see if it doesn't suck so much this time. :)
 
Here it is. The two outside walls have two layers of 1x4s and 1/2" drywall. the interior walls are 2X4s. There is no insulation. Ceiling height is 6'-11 1/2" to the bottom of the 2X10 floor joists. (I would like to know why anyone would ever build a 7'-2" concrete foundation wall?)

The ceiling has a plastic channel drop ceiling that is tight to the joists with wood fiber acustical 2x4 tiles. No insulation up there either, and to access the joists, the whole contraption will have to be disassembled piece by piece and after removing a couple for wiring, I would say they will all be ruined.

I have to build a 2x4 fur wall to insulate the outside walls and plan on leaving the crap that is hanging there already. My specialty as a carpenter seemed to be building curved walls, so give me some ideas. My next cad try will be waves. :)

By the way, the room is disassembled for ground seepage damage, so sorry, no pictures and I have never had a stereo down there either.

roomdiagram-AsIswalls3D.jpg


roomdiagram-AsIswalls2D.jpg
 
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I say throw your curved wall back into the model, along with the waves and just put them on a separate layer. Somebody here has to be able to analyze it the way you want...
 
Ok, just finished reading this pdf from the sub-woofer thread again. I guess maybe I better draw up multiple 2x2 stud walls,spaced 3 1/2" apart with the 2x2 studs spaced 3 or 4 feet on center, covered with 1/4" drywall and R-11 fiberglass crammed inbetween?

Double stud rows are for improving acoustical separation between spaces. Are you worried about sound being heard in the spaces adjacent to your listening room? If not, then you shouldn't need to worry about double or staggered studs.

I will try to take a look at your room later today. Hopefully some of the other guys will as well and you'll have multiple opinions to work with.
 
The two outside walls have two layers of 1x4s and 1/2" drywall.
By this do you mean there are 2 1x4s flat against each other, than used as studs for a furring wall off of the concrete walls?


I have to build a 2x4 fur wall to insulate the outside walls and plan on leaving the crap that is hanging there already.
If there's already a furring wall, you should take it down, or at least knock big holes in the existing drywall. If I understand, what you're proposing is drywall - airspace - drywall -airspace - concrete. That's actually not as good of a wall as drywall - bigger airspace - concrete. The bigger airspace will allow your walls to absorb lower frequencies. And you can sometimes get some weird resonances when you have two thin airspaces coupled like that (this is more of a concern if you're relying on the wall to provide isolation, which I understand you're not in this case).
 
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Sorry, I ment multiple stacked thin walls. Layers of 1/4" sheet rock, each on their own isolated wall to act like a bunch of bass absorbing membranes to isulate the concrete wall behind.

So, a layer of 3.5" fiberglass against the existing drywall, then a 1.5 stud wall(2x2 studs @ 24, 36, or 48" o.c.) crammed against that, a layer of 1/4" sheetrock, another layer of fiberglass, and than another layer of 1.5" stud wall crammed against that and then the last layer of sheetrock.

So depending how tight I can compress the insulation, I might only lose less than 5 inches of room on each wall (A fur wall would be 4 inches). In the end, the whole contraption will probably bow out in the middle, but that shouldn't matter.:)
 
By this do you mean there are 2 1x4s flat against each other, than used as studs for a furring wall off of the concrete walls?

One set of 1x4s nailed horizontaly to the concrete walls @ 24" o.c. with the second set nailed verticaly to those @ 16" o.c. and the sheetrock nailed verticaly to those.
 
So, a layer of 3.5" fiberglass against the existing drywall, then a 1.5 stud wall(2x2 studs @ 24, 36, or 48" o.c.) crammed against that, a layer of 1/4" sheetrock, another layer of fiberglass, and than another layer of 1.5" stud wall crammed against that and then the last layer of sheetrock.
I really wouldn't do that. Multiple layers of drywall separated by stud rows won't don't anything for you. You're better off with a thicker air space. Really, I think your best option is to tear out the existing furring (or knock really big holes in the existing drywall) and built out a new, single layer furring.

You can definitely leave the horizontal 1x4's in place, they won't hurt anything. You can leave the vertical ones in place, too, if it's too much trouble to tear them out. You just don't want to leave that existing layer of drywall because it's robbing you of airspace.

Compressing more fiberglass into a smaller space doesn't improve its ability to absorb sound or, as far as I know, insulate against heat transfer. It's not the fibers that trap sound and heat, it's the air that's stuck between the fibers. Compacting it might even reduce its effectiveness.
 
If there's already a furring wall, you should take it down, or at least knock big holes in the existing drywall. If I understand, what you're proposing is drywall - airspace - drywall -airspace - concrete. That's actually not as good of a wall as drywall - bigger airspace - concrete. The bigger airspace will allow your walls to absorb lower frequencies. And you can sometimes get some weird resonances when you have two thin airspaces coupled like that (this is more of a concern if you're relying on the wall to provide isolation, which I understand you're not in this case).

Ok, I understand. I'ts just like my old next door neighbor always said, "James, a little knowledge is a dangerous thing!"
 
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...



Compressing more fiberglass into a smaller space doesn't improve its ability to absorb sound or, as far as I know, insulate against heat transfer. It's not the fibers that trap sound and heat, it's the air that's stuck between the fibers. Compacting it might even reduce its effectiveness.


^That's true. Compressing fiberglass insulation reduces it's insulation value.


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