Ok, so it’s not really magic at all. But would you have started to read a piece with the title “Modeling”? In this Tech Corner, I am going to explore the various kinds of modeling software. I will also introduce you to Danley’s modeling software DIRECT™
he study of acoustics provides some interesting challenges. One of these challenges is the fact that you can’t see sound… at least most of the time! The man who is considered to be the father of modern acoustics, W. C. Sabine (1868-1919), actually used a technique called Schlieren photography, a technique that makes disturbances in the flow of fluids visible, to take photographs of how sound behaved in scale models of rooms. Before the advent of computers, architects and acousticians would build scale models of important projects like concert halls to try to ensure that they ‘got it right’. These scale models, often 1/20 or smaller, were very carefully constructed and measured using sounds that were shifted up in frequency to compensate for the scale. Even though these were expensive models to build and required very time consuming and difficult measurements, the results proved extremely valuable in the development of concert halls and also in our understanding of architectural acoustics.
As computers became more powerful and available, they began to be used for acoustical models to the point that now models can be built and virtual sound systems placed in them. Using a process known as auralization, users can listen to the virtual sound sources in the virtual rooms!
Currently, modeling programs fit broadly into two categories: Acoustical modeling
programs and Direct field mapping
programs. Let's look at the acoustical modeling type first.
There are a number of very powerful software packages currently available. The most popular are CATT Acoustic™
. All of these programs can be used to create three-dimensional acoustical models of spaces and have the ability to do auralization. These are not inexpensive tools. For most of us, we will need to carefully consider not only which one to use, but whether they should be used at all.
It is important to understand what these programs do. They take data in, process it, and put data out. (duh) OK, firm grasp of the obvious! But it bears a bit of reflection—no pun intended.
First, let's look at the data. In every computer model, there are 2 kinds of data. First, there are the data that the user provides: the size and shape of the room and all of its furnishings. Obviously, this is the point many compromises are made and should be. The results you get out are only as good as the model! In acoustics, this means making lots of decisions about how much detail you are going to include in the model. The more detail, in general, the more accurate the results, but the longer it will take to input the data and for the software to run. The second type of data is provided by the software itself. When you build a room in one of these programs and you place a virtual loudspeaker in the room, you are trusting that the loudspeaker data are accurate. When you tell the software that a certain area of a wall or a floor is covered with a certain type of drapery or carpet, you are trusting that someone somewhere actually took the time to accurately and correctly (you can be accurate and incorrect) measure that drapery or carpet, and that those data are correctly implemented in the algorithms of the software. A few years back while I was still teaching, one of my students asked a very interesting question, “how good are the acoustical data in the database used by a certain acoustical modeling program?” She used this question as her senior project focusing only on the carpet database. She discovered that the carpet data was about 40 years old and she could find relatively little current data on carpet acoustics. Her measurements of carpet data often did not track with data in the software. Interesting!
That brings us to the “process” part. Each modeling program uses different algorithms to predict the acoustical performance. Some are better than others. There is a fair agreement between the various software packages that I have examined, but not full agreement. Delving into the higher math or the code is beyond most of us mere mortals, but the user/buyer should be aware that this is not by any means an exact science.
The third function is, of course, the output. Remember that software gives you data, processed data. It does not give you ANSWERS.
That is to say, it won’t tell you if the speaker you selected or the treatment you selected or the basic design of the space is GOOD
. A human brain is required for that step. So, when evaluating software, how the data are presented to you for your brain to process is very important. If the graphics don't make sense or are hard to read, it will be that much more difficult to process the information.
DIRECT FIELD MAPPING
A number of loudspeaker companies, including Danley, have created mapping programs that, for many, are an alternative to the full-blown acoustical modeling programs. A direct field mapping (DFM) program does not do acoustics! These programs do not evaluate how loudspeakers will interact with an acoustical space, but they can give you a very accurate picture of how the loudspeaker will cover a certain audience. Once again, they are only as accurate as the data put into them. One big difference is that in the DFM program the user only inputs room information. Since the room is not part of any calculation, it is there for visual reference only. The accuracy and reliability of the software is really a function of the data that are part of the program.
Most if not all of these DFM programs are free to the user which is good, but they only let you use loudspeakers from the authors’ company, which for many is a problem, especially if you are trying to compare brand A to brand B. Well our answer to that is to always use brand D! (sorry – couldn't resist)
Our program is called Direct
. It is a fully 3D mapping software – many of our competitors are 2D only. It is the brainchild of our genius programmer Sebastian Rivas – Godoy (with a little input from yours truly). It is 4 years old this year, and we just released version 2.1. We have tried very hard to make Direct the best program of its kind. It is very fast, very intuitive, very powerful and free! It is difficult, if not impossible, to fully describe software in print, so I will not go into much detail here. I have produced a whole series of training videos for Direct and I also conduct online training.
Direct runs on both MAC and PC and the files can be exchanged between them seamlessly. It uses Sketchup as a drawing environment. That means that you can create your own buildings in Sketchup, or if you have DWG/DXF drawings you can import them into Sketchup, then export them into Direct.
Before I leave you, a word about accuracy and reliability. When I was a professor developing curriculum for teaching modeling, I insisted that the curriculum involved what we called closing the loop. It is my considered opinion that everyone who uses modeling software of any kind should, from time to time, measure the final product and compare it to the model. We at Danley do that all the time in our large projects. We encourage our dealers to close the loop as well. Designing a system for your church, great. Model it, install it, then compare the installation to the model. Since Direct is not an acoustics program there are things it cannot predict, but it should be pretty accurate in predicting coverage and to a degree levels. Outdoors it will even be better. If there is agreement fantastic! There should be! That should serve to build confidence in Danley and of course in Direct. If the two don't agree, please take the time to try to figure out why.
As always feel free to contact us at Danley Sound Labs. I would love to introduce you to Direct
Registered trademark of CATT Acousitc
Registered trademark of Bose Corp.
Registered trademark of AFMG Technologies GmBH