In March, EMPAC featured the world premiere of a new work for voice and electronics featuring soprano Amelia Watkins, utilizing the wavefield synthesis loudspeaker array. The concert featured live voice, 512 channels of processed vocals, and spatialized electronic sound. It was the first public performance utilizing this new sound system, developed by the engineering team at EMPAC. Photo credit: Mick Bello
The Curtis R. Priem Experimental Media and Performing Arts Center (EMPAC) at Rensselaer recently debuted a unique new system that explores the relationship between sound and space. “Think of it like a pebble dropping into a pond,” says EMPAC’s lead audio engineer Todd Vos, describing the way a sound wave emanates from a speaker head. Now picture 500 tiny speakers arranged in a continuous ring around the room. As every one of those speakers casts sound into the room, the waves overlap and intersect, creating a dense, three-dimensional, immersive sound environment for a listener to explore.
This is a simple way to imagine the effect of “wave field synthesis”; the math behind the concept is significantly harder. Even harder is the process of constructing such a system, of which only a handful exist in the world. This month, EMPAC finished construction on a new wave field array and is beginning to explore applications of the technology in artistic production and audio research. An April 21 talk by Paris-based audio research center IRCAM researcher Markus Noisternig will give students and the public an opportunity to interact with the system and learn about this novel technology of sound spatialization.
This type of innovation is an example of Art_X at Rensselaer, a new initiative designed to help Rensselaer students discover the art in science and technology, as well as the science and technology in art. Art_X is about the intersection and union of heretofore disparate disciplines and about the fact that unexpected perspectives yield unexpected insights.
In bringing artists and researchers together in deeply collaborative engagement, providing them the opportunities and support to explore together the art and science of the mind, as well as the art and science of matter, Art_X helps define The New Polytechnic—a new paradigm for teaching, learning, and research at Rensselaer. The New Polytechnic enables collaborations between talented people across disciplines, sectors, and global regions, in order to address the complex problems the world.
Picture 500 tiny speakers arranged in a continuous ring around the room. As every one of those speakers casts sound into the room, the waves overlap and intersect, creating a dense, three-dimensional, immersive sound environment for a listener to explore.
“I’ve been involved with the synthetic localization of sound sources since 1972,” says Johannes Goebel, EMPAC director, who tasked Vos and his team with the construction of the array. Throughout his career, Goebel said, “I’ve always been highly interested in how the localization of sound can be used as an artistic means.” Space is not often considered as an element of musical composition, on a level with melody, rhythm, and timbre (the “color” of sound). But to a composer with access to a wave field array, the spatial depth, proximity, and movement of sounds can be just as powerful.
To distinguish wave field synthesis from other more-common types of surround sound, Goebel uses a photographic analogy. Most audio systems create something like a snapshot of sound, mixing discrete elements together to imitate what is heard in real life. Wave field synthesis actually models the sound environment in its full complexity—more like a hologram. Within the wave field, there is no “sweet spot” where the mix is just right; one may actually move around in the sound space and find equal resolution in all places, the same as if one were to walk around a concert hall during a live performance.
What is significant about EMPAC’s new system is the very small size of the speakers and their very close proximity (5 centimeters apart). This allows the system to integrate a higher frequency range into the wave field (up to 6 kilohertz). This high range is important because it is the higher frequencies of human hearing that allow us to spatially locate the source of sounds around us. (In contrast, think of the more generalized, enveloping effect of deep bass.)
Another innovation realized by this system is its modular construction. The speakers are divided into 16 boxes that can be configured in a range of ways and can be set up and taken down quickly (unlike most systems that are installed permanently into theaters).
What is significant about EMPAC’s new system is the very small size of the speakers and their very close proximity. This allows the system to integrate a higher frequency range into the wave field. This high range is important because it is the higher frequencies of human hearing that allow us to spatially locate the source of sounds around us.
Due to the customized nature of the hardware, there is, as of yet, no standard wave field software available to run such a system. In the first phase of testing, it required four computers to operate all of the channels through synchronized versions of MaxMSP, a common platform among electronic composers. Enter IRCAM. The prestigious audio research center has developed wave field-specific software and will be working with EMPAC to streamline this process. Noisternig’s visit will initiate this exchange.
In late March, Rensselaer graduate arts student Zach Layton took the rig for its first test drive. 512 Voices is a choral composition that used the voice of soprano Amelia Watkins to generate the effect of a full choir, situated around the audience, who were encouraged to move around in the space. Layton had worked on other multichannel systems, including the smaller wave field array run by Jonas Braasch, associate professor of architecture, and the CRAIVE lab, but this project allowed him to expand the scope of his work by several orders of magnitude. “What I like about these holographic environments,” Layton says, “is that they don’t alienate people from the physical space” the way virtual systems do. This allows the composer to create what he calls “morphing, shifting landscapes of color, a kind of perceptual geography.”
This echoes Goebel’s insistence that what is truly interesting about the technology is not its ability to replicate real acoustic spaces but rather to “take the clay out of the ground and create a new sculpture.” To this end, the wave field system will figure heavily into EMPAC music curator Argeo Ascani’s future programming. Between now and October, several multichannel electronic composers will be in residence at EMPAC to work with the system with the goal of developing new pieces that can only be performed on such a system. A fall collaboration with the Montreal-based Akousma Festival will underscore the efforts.
Markus Noisternig will speak about “Modern 3-D Audio Technologies and the Relationship Between Sound and Space” on Thursday, April 21, at 4 p.m. in EMPAC Studio 2. More information.
