Next Year's Model

Computers play a major part in the design of new buildings and their sound systems. A standard component of the planning process is the acoustical modeling software that allows the sound reinforcement system design to be developed while the building design is still on paper (or its CAD equivalent). The acoustical model can provide insight into the rooms acoustics, the loudspeaker system performance and even the interaction between loudspeaker and microphone. It also provides another method of learning how new loudspeaker technologies will sound and how the room acoustics will affect their performance.

Experience with computer models of sound systems can provide considerable insight into the limits of some loudspeaker systems and the advantages of others. The computer model, alone, is no more useful in designing a good sound system than a word processor is at writing a good novel. It requires an extensive period of creating computer models, which are then built (or already built) and comparing the results of the actual system with those in the model. For the experienced computer model builder, the results can even reduce the time required to adjust the final loudspeaker components. An knowledgeable user can develop loudspeaker aiming information in the model that offers very accurate settings for the field crew to follow that will be within a few degrees. The latest areas of modeling include the ability to experiment with the frequency shading and relative timing of loudspeaker array elements to steer the sound from a loudspeaker cluster.

No one should expect to design loudspeaker arrays within a computer model if they haven't had previous experience with installing, aiming and optimizing loudspeaker arrays in the field. Many of the practical issues of horn collisions, orientation and rigging cannot be understood from within a computer model. Only after you have been successful at making loudspeakers stay put at the right tilt and splay angles, can you understand the need for this practical experience. On the other hand, only through computer modeling can you learn how many common loudspeaker configurations achieve very poor acoustical performance, thus leading you to look for alternative configurations that don’t suffer from the "boxes-slammed-together" destructive acoustical interference. The computer model allows you to explore configurations that would take weeks to configure and evaluate in a physical space.

The auralization of the computer model is the final step in evaluating contentious acoustical treatments or sound system configurations. While the sound quality produced by a computer model is not an exact reproduction of the sound of the installed system an informed user can use this process to highlight the importance of specific acoustical treatments, room shaping issues or loudspeaker configurations. This ability to provide an audition of the differences between very technical criteria, allow those only interested in the end result to make informed decisions on the trade-offs under consideration. Once they have heard how poor the invisible (hidden out of sight and earshot) loudspeaker sounds compared with the visible loudspeaker (that is correctly located for acoustical performance) they can then decide based on more than just the visual effect.

There are two computer modeling software programs that are widely distributed in North America. The best known is EASE from ADA - Acoustic Design Ahnert of Germany (www.ada-acousticdesign.de) and distributed by Renkus-Heinz (www.renkus-heinz.com). This program has a broad range of acoustical analysis tools and features the largest library of loudspeaker modeling data of any software, with 33 (at my last count) manufacturers represented in the database that ships with the program. This is the program I have been using for many years on a regular basis to develop and analyze the sound system performance and room acoustics of new and existing buildings. It provides me with a practical interface to build the 3D model of the room, analyze the critical acoustical parameters and optimally locate loudspeakers.

Lesser widely known is the program, CATT-Acoustic from CATT in Sweden (www.netg.se/~catt). The program is distributed in North America by RPG® Diffusor Systems (www.rpginc.com). This program focuses on acoustical design and auralization, rather than loudspeaker system design. There are a few other acoustical academic and proprietary programs that provide modeling and analysis of room acoustics and loudspeaker performance, including some very simple programs intended for loudspeaker layout in the design of paging systems and background music applications.

Computer modeling software will not allow you to implement new loudspeaker designs without other corroborating experience with the device, but it is a very useful way to add another view into the performance of the unit. Combined with listening tests and field measurements, computer models provide an excellent way to investigate the best way to implement loudspeakers and locate the acoustical treatment. Testing the effects of room shapes and how they interact with the loudspeaker system is never as easy when you must use the big, expensive full-size model.

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