A cellist was playing on stage at EMPAC’s main theater on Friday afternoon, performing a lovely, lilting snippet of an early Mozart string quartet. You could hear it – there, just by your right ear. When you stepped to the right, it stayed put. When you walked to the left, you passed by two violins and a viola.

Only you didn’t. Not really. The music was audible, formed from sound waves as present and real as any you’d hear from a live string quartet, but the ensemble itself was a ghost — its music recreated in a system called Wave Field Synthesis that generates sound waves in real space from a long array of speakers several feet away. Essentially, the array functions like a ventriloquist, throwing the elements of sound and reassembling them at a distance.


“It’s synthetically, actually there – it’s synthetically the same as if it was there, but (there’s) no body there,” said EMPAC music curator Argeo Ascani. “It’s really, really, really, really hard for your brain to understand – and it kind of feels like magic.”

The Wave Field equipment onstage was one of two innovative 3D-audio systems on display in at a media event Friday afternoon, as Ascani and audio researcher Markus Noisternig demonstrated some of  the more mind-blowing basics of emergent technologies that expand – and alter – the nature of recording and projecting sound.

“The sound exists. It’s physically there,” said Ascani of Wave Field Synthesis at the media demo, which was organized to mark EMPAC’s inaugural “Spatial Audio Workshop” for composers and programmers working within “holophonics” –  i.e., immersive sound technologies, akin to acoustic holograms, that create an aural environment from hundreds of loudspeakers.

Kicking off on Monday, the five-day international workshop is a collaboration between R.P.I., the Paris-based Institut de Recherche et Coordination Acoustique/Musique – the globally prominent audio research hub where Noisternig works – and Harvard’s Studio for Electroacoustic Composition. Many of its roughly 40 international participants will take part in hands-on afternoon workshops exploring both Wave Field Synthesis and  EMPAC’s other spatial-audio system, High-Order Ambisonics, which records sound from multidirections that can then be replicated and tweaked in three-dimensional playback via numerous speakers.

In an Ambisonic recording, sound moves — traveling from speaker to speaker in quicksilver adjustments that duplicate the behavior and characteristics of sound in space. In demonstrating the system, Noisternig played a few excerpts of multichannel recordings via 64 large speakers ringing the upper reaches of the EMPAC theater.

In one, an abstract work by Natasha Barrett titled “He slowly fell and transformed into the terrain,” a series of whooshes, dings and grating mechanical noises clanked around the theater with unnerving realism, lending the space the eerie, alien feel of a dystopian sci-fi movie. In another, “Le Encantadas” by Olga Neuwirth, the recording evoked the sounds of an echoing cathedral – its oohing voices and blaring horns popping out in different pockets of the room.

They all sounded real – or real enough, at least, that the reflex to turn and look proved irresistible. Just as the cellist wasn’t there, neither were all those clangorous sounds and ethereal voices. There was nothing to see. But inevitably, journalistic heads turned to track the emergence and movements of each one.

Developed over several years, the spatial-audio systems in use at EMPAC premiered with a soft opening last August, when R.P.I. Professor Rob Hamilton performed “108 Troubles” on a Disklavier piano — the sounds traveling among each of the system’s small, controlled speakers. Upcoming public performances featuring spatial audio include two next week by workshop leaders Noisternig and Harvard professor Hans Tutschku. In September, EMPAC will use its systems in a theatrical context with Andrew Schneider‘s “After.”

 Noisternig said researchers anticipate that new audio technologies may ultimately have applications beyond the performing arts — equipping cochlear implants, for example, with a directional component in sound amplified for the hearing impaired.  

 “We know that human hearing is very focused on three dimensions, because it’s one of our primary defense senses, actually,” he said. “Because I can’t see who’s coming behind me. But I can hear it, and localize it. . . . So there are many applications away from art.”

If you go
Upcoming multichannel performances featuring EMPAC’s “spatial audio” systems
Where: EMPAC, 110 8th Street, Troy
Info: 276-3921; empac.rpi.edu

Markus Noisternig
When: 7 p.m. Monday, July 10
Admission: Free

Hans Tutschku
When: 7 p.m. Thursday, July 13
Admission: $18 general; $13 for senior citizens, non-R.P.I. students and R.P.I. faculty and staff; $6 for R.P.I. students with I.D.

(The Spatial Audio Summer Workshop, which runs from July 10-July 14, also offers admission to all morning lectures for $150.)