How often have you wondered what a room was going to sound like before it was built? How would it sound if the walls were parallel and not canted? Are all of the acoustical room finishes really required? Will there be echoes? Is the reverberation time too long? What will speech sound like in the room? What will music sound like?
Much has been published on this subject in recent months. A major consumer loudspeaker manufacturer has developed a system to model a room with their loudspeakers. However, at Thorburn Associates, we have been working with this type of technology for over 2 years and have begun offering Binauralization™ as a service to our clients.
Prior to Binauralizations™, modeling was used primarily for large and extremely critical projects such as concert halls. The only way to acoustically model a space was to build a scale model of the room. This is tedious and time consuming. To build an acoustically accurate scale model, the details, the relief, and even the construction materials must be scaled down to match the appropriate acoustical effects. Because the sound waves that we hear range from 56 feet to 2/3 of an inch in length, it is difficult to find materials that accurately scale down to 1/10 inch or 1/4 inch scale models.
Unlike model building for visual aesthetics (where a red barn looks like a red barn) we can’t just paint the surfaces to create the same scaled visual look. We must also scale the acoustical characteristics of the materials used. Computer simulations allow us to address the problems of the scale in a much more effective manner.
Also, unlike scale models, where complex charts and numbers are used to represent the acoustical properties of the room (Figure A), Binauralizations™ let you hear for yourself if the finished project will sound good or bad.
Figure A. Complex Graphics are no longer necessary to understand the Acoustical Characteristics of a room when using Binauralizations TM.
Some of the questions that always arise when we discuss this new technology with clients are “How accurate is the model?” “Can we adequately rely on what we hear in the computer simulation to reflect what will actually be built?” and “How can we use this new technology to better serve our clients?”
Does it Work?
Prior to offering Binauralization™ as a service, we modeled a number of different spaces, then conducted binaural measurements once construction or retrofitting was completed. What we found is that while it is very difficult to achieve an exact model of the room, the major issues that we, as acoustical consultants, are concerned with and need to communicate to the owners and architects, are very readily apparent. So, yes, it does work!
The first step in developing an acoustical simulation is identifying the finishes within the room, both in type and location. Once the physical characteristics of the model are defined, random rays are sent out from a source location. (Figure B.) These rays simulate sound waves leaving the source and traveling in the room. As the rays hit a surface, the computer determines how much acoustical energy is absorbed by that surface, how much energy is reflected, and in what direction.
Figure B. Single Ray Tracing showing how sound is both absorbed and reflected throughout a space.
This process continues until the sound ray has traveled a predetermined length of time. The longer we let the calculation go, the more accurate the model. Accuracy is also increased with the number of rays sent out.
With this information in hand, we then post-process audio from a CD or tape or a recording of your own voice, and let you listen to that sound from a specific location in the room.
How Can I Use Binauralizations™?
After the model is built, we can readily change surface materials to allow you to hear just how bad an echo will be if we don’t treat the walls or determine if you need to have an acoustical tile ceiling, prior to construction. Binauralizations™ allow the client to make a subjective decision without relying on us to “verbalize” our recommendations in a meeting or with a report.
We can model any type of facility from churches to theatres to conference rooms to lobbies to casinos to entire theme-parks! Binauralizations™ are for any project where good acoustics are necessary and bad acoustics can ruin its success!