Credit: Courtesy Bose
THE TUG-OF-WAR BETWEEN A room's acoustical optimization and its visual aesthetics is often a thorn in the respective sides of the AV designer and the architect. When working in new construction especially, all the various “what-if” scenarios of sound system design can drive a person mad.
Technology has made it easier for architects and AV pros to reach across the aisle. Just as the former has long-enjoyed computer-aided design, the sound system designer now enjoys computer aid of his own. For the audio industry, auralization offers a tantalizing proposition: The ability to listen to a room before it's built.
“Auralization is the technique of creating sounds from data, which can stem from measurements or computer simulations. This is equivalent to what is known as a visualization or animation in computer graphics, video, and television technology,” explains Dr. Michael Vorlander, a professor at the Institute of Technical Acoustics at RWTH Aachen University in Germany, and author of the book Auralization: Fundamentals of Acoustics, Modeling, Simulation, Algorithms and Acoustic Virtual Reality.
“Using auralization, sounds can be created that are virtual, not recorded in a real environment,” Vorlander says. “These sounds can represent things like environmental sound or noise, speech and music, and the effect of sound in the environment, buildings, vehicles, aircrafts, offices, classrooms, concert halls, and any other [place] where perception of sound plays a role.”
According to Vorlander, the technique of auralization originated with room acoustic predictions and simulations on concert halls and opera houses prior to construction. The applications have since expanded to many other venues.
“The purpose is common to all applications: analysis and optimization of acoustic conditions during a design process,” he says. The users of auralization technology include architects and acoustical consultants, plus design engineers in the automotive and aircraft industries, as well as others engaged in product development. “Products in this respect are all devices which create sound or noise, such as hair dryers, shavers, household appliances, HVAC systems, washing machines, dishwashers and so on,” Vorlander says.
Pat Brown, president and owner of audio education firm Syn-Aud-Con, says, “System designers have long relied on charts and plots to display predicted system responses. Auralization adds another dimension, allowing the designer to listen to the data.”
CONNECTING THE DOTS
Room data for auralization is based on its predicted room impulse response (RIR). It should be noted that the techniques and methods to obtain a predicted RIR are varied and plenty. There are differing philosophies on how someone can obtain “accurate” room data for a room or structure that does not yet exist. In an existing space, a measured RIR is produced by creating an impulse (hand clap, noise generator, etc.) in the room and measuring it at selected listening positions.
“The process of convolution allows echo-free, or anechoic, speech or music to be encoded with the RIR. So, I just need a good RIR and then I can listen to drums, piano, or vocals,” says Brown. Convolution is the encoding of anechoic program material with a measured RIR.
“Auralization is the encoding of anechoic program material with a predicted RIR,” Brown continues. “Today, an auralization can be virtually indistinguishable from a convolution, and that has been the goal of the technology from day one.”
Vorlander likens the benefits of auralization to the uses and benefits of visualization. “For example, the interior design for a living room, kitchen, or office is usually done by showing the arrangement of furniture and the choice of colors on a computer, in order to visualize how it will look. In auralization, the benefit is that the product or design is made audible in a way that designers and clients can experience how it will sound. In commercial applications, auralization is part of rapid prototyping, the method of developing a new product with the least possible prototype construction, which saves cost and time,” he explains.
In the audio industry, auralization aids in the selection and placement of loudspeakers within a space, and is often a catalyst for a discussion with the architect about how acoustical treatment, finishes, and room design will affect the acoustics and sound system performance.
“The holy grail of sound system design has been to know what the finished system will sound like in advance. Auralization brings this a step closer,” says Brown.
Ultimately, the architect benefits because room changes can be made before actual construction. The acoustician benefits because he can make better decisions regarding acoustical treatment selection and placement. The clients benefit because they spend their money wisely, and the end-user benefits because the room and the system will sound better. In theory, everybody wins.
“Auralization is a great tool for negotiation,” says Morten Jorgensen, manager of tools and applications for Bose Professional Systems Division, “Today's buildings are visually spectacular, built with glass, steel, and concrete—all hard surfaces that are not good for acoustics. Now the architect, systems designer, and client can hear what is or isn't good with the acoustics and can make a decision on which sound absorption works better.”
Such decisions have traditionally been made based on cost rather than performance, because until auralization, performance data has been hard to interpret.
FUZZY MATH
The Bose Auditioner Playback System III is a portable device that allows people involved in a project to listen to a convolved audio output in any location.
But even in the best win-win situation, the formula for applying auralization technology can be unclear. That's because there exists differing schools of thought on how to determine the properties of surface materials, for example, as well as the parameters of the auralization process. In short, there is no how-to checklist that applies to every situation.
“There is no common application for auralization because the simulation tools are very specific, and they depend on the acoustic problem,” says Vorlander. “The reason for this is the big variety and the difficult physics of sound problems. Sound field physics, for instance, can be relevant in environmental noise on scales of miles or in the ear canal of the eardrum on scales of inches. The mathematical equations and the computer models are, thus, very different.”
Several major companies worldwide have worked to further the use and development of auralization technology, including CATT-Acoustic in Sweden, Odeon in Denmark, SDA Software Design Ahnert (developer of EASE and EASE EARS) in Germany, and Bose Corp. in the United States. In academia, research universities continue to address the science of sound simulation, vibration generation, and sound transmission.
“These problems are partly very difficult,” says Vorlander. “The scientific community in acoustics is driving simulation and auralization by developing calculation models for such problems.”
Vorlander believes auralization is still in the beginning of its evolution, in part because only recently have computers become sufficiently powerful to solve acoustic problems in large spaces such as concert halls, or in complex systems such as cars. “The technology will advance with the extension of knowledge about sound perception and sound design [psychoacoustics],” he explains. “It will be changing in a way that more and more complex problems will be solved. Advances in the development of auralization will be achieved through interdisciplinary collaboration [among] physicists, engineers, and psychoacousticians.”
Jorgensen harkens back to 1986 when Bose Modeler sound system software was essentially “a fast calculator.” As the technology advanced, a sound designer could create several system designs for the same room, and although the systems might look good on paper, they still didn't sound right to the ears. “Auralization gets your ears involved in the design process,” he says.
Launched in 1994, the Auditioner Playback System from Bose focuses on user interactivity, with the ability to change a loudspeaker or acoustic materials and listen to the results in seconds. Jorgensen notes that accuracy is also a constant point of improvement. “If it were just pretty pictures and graphs, then it is just an expensive computer game. The decision in the virtual room should be the same as in real life,” he says.
EASE was first introduced in 1990 by Dr. Wolfgang Ahnert in an attempt to bring more accuracy to acoustic design and modeling. Shortly after, in 1993, EARS debuted as the listening tool to work in conjunction with EASE data. Renkus-Heinz, an audio manufacturer in Foothill Ranch, Calif., is the sole distributor of the English version of EASE and its related products.
Recently, Bose system designers used Auditioner technology to predict how a system would sound in the company's own 350-seat corporate auditorium. “In the past, we would have visited other auditoriums and seen what works or doesn't work. It would have been a copy and paste of design,” says Jorgensen. “With Auditioner, you can play with walls and other materials that you can't change in real life, like the sound difference between a 12-degree wall versus a 15-degree wall.”
In what is perhaps another step in evolution, Bose introduced the Auditioner Playback System III in 2005. The proprietary system addresses the need for portability because, says Jorgensen, “The people who benefit from the technology are not all in the same place.
“The Auditioner Playback System doesn't use headphones so it eliminates in-head localization of the sound,” Jorgensen continues. “Instead, there is a chin rest and the user sticks their head into the playback device. It puts you in the middle of the soundfield instead of seeming like the sound is coming from inside your head.”
LOOKING AHEAD
Jorgensen thinks that over the years auralization will become more integrated into a building's design process. He notes that advances in architectural modeling software that allow a user to conduct a walkthrough of a virtual space will spur improvements in acoustical modeling and auralization.
Brown says, “Today's powerful processors allow auralizations to be produced in fraction of the time that it took just a few years ago.”
A recent CATT-Acoustic innovation allows the virtual listener to wander around a room while listening to the sound system. Photo-realistic room graphics can supplement the listening experience.
However, certain factors currently present barriers to widespread adoption. The first is economics. “Designers can always make their designs better, but any added time can, by some, be perceived as additional overhead,” says Jorgensen. “With so many iterations available to a design, it can be time-consuming.”
The second factor is ease of use. “The learning curve is steep for several reasons,” says Brown. “First, the predicted RIR will only be as good as the room modeling technique of the user. The required knowledge base includes acoustics, electroacoustics, and CAD skills.”
It takes study, practice, and discipline to become proficient at room modeling and auralization, Brown says, “but the dividends are well worth the effort.”
Linda Seid Frembes is a freelance AV journalist and frequent contributor to PRO AV.