by Warren Singh-Bartlett
A passionate audiophile who grew tired of today’s tinny sound, Princeton professor Edgar Choueiri is determined to bring high-fidelity sound to brand new depths.
Naturally, my conversation with Edgar Choueiri begins with space. I’m sitting in the Lotos Club in New York’s Upper East Side, waiting to talk to the doctor about the evolving field of 3D audio but almost immediately, we end up talking about ion engines, the Chinese settling on the moon and mining rocket propellant from asteroids.
It isn’t entirely unexpected. Dr. Choueiri is a man who wears (at least) two hats. Based at Princeton University, he currently runs two entirely different labs. The first is devoted to his professional passion – space – and more specifically, the creation of ever more refined ion propulsion engines. The second results from a personal passion – music – and is devoted to the reproduction of three-dimensional sound.
Wait, isn’t that what a Surroundsound system does? I certainly thought so but apparently, the answer is no.
“So suppose we record a conversation here,” Choueiri says, as we tuck into lunch at the Club’s private dining room, “we record sounds from where they are made, so people walking towards you talking would not just sound closer and closer, you‘d actually be able to track them getting closer and closer. That’s 3D sound.”
Confused? I’ll admit, I was. At first. But you see, all amplified sound, including Surroundsound, stays in the speakers. As anyone with a system at home knows, Surroundsound is great for effects, explosions, cars careening across the screen, that kind of thing. By using several speakers, panning the sound between them and adding reverberation, Surroundsound can give the illusion of depth.
What it cannot do, though, is accurately place sound in space. Why does that matter? Well, it can make it sound as though the car has driven from one side of the room to the other, but it can’t tell you whether the car’s in front of you or behind. Real 3D Sound could. In fact, a character could walk towards you and whisper directly in your ear. And only your ear.
Time for another confession. Ever since I developed a fleeting passion for *cough* mind-altering substances back in college, I’ve been intrigued by the possibility of being immersed in music. Choueiri’s solution promises exactly that.
First, some science. Humans locate sound using different cues. There’s volume, then there’s the way a sound made to one side of your face sounds louder that side than on the other, there’s the way a sound takes a little longer to reach one ear than the other and finally, there’s refraction, the way sound will have bounced off different parts of your body before it reaches your pinna.
The pinna is central to 3D. Not just because it transmits sound to the brain but because every one is unique. Each one of us hears slightly differently.
Technicians have known this for decades – the first attempts at reproducing 3D sound date to the 1880s. The problem is not capturing it in 3D. The binaural recording, for example, does an excellent job of that. The problem is reproducing that sound effectively afterwards. The brain, you see, is a master at pinpointing sound sources. It’s what enabled our ancestors to hear from which direction the sabre-tooth tiger was pouncing and it isn’t easily fooled.
To date, most solutions were either too unwieldy or only really worked through headphones. And then, only if you didn’t move your head too much but once a recording is played through speakers, the overlapping soundwaves, known as cross-talk, reduces even binaural to mere stereo.
Enter Edgar Choueiri and his BACCH Filter. When plugged into your stereo system, this briefcase-sized box plays not only 3D sound but does so in a way that is optimised for your ears only.
Drawn to the problem by his love of music, Choueiri began tinkering with solutions in his spare time. Realising the solution was digital, not mechanical, he found himself being drawn in. It was inevitable. A passionate mathematician and audiophile, with a marked preference for analogue over digital (“If you’d told me in the 1970s that in 30 years, a music format that sounds ten times worse than what we had then, so devoid of fidelity, would become the standard, I’d have laughed”), this pursuit became personal. When he finally cracked it, even he wasn’t sure he was right.
“It worked on paper. The algorithm suggested I could reproduce 3D sound without any colouration. But I was sceptical, so I stayed up all night, checking and rechecking my calculations.”
When he was sure, he put his algorithm into practice. It worked. Realising his invention’s potential, he turned to Princeton for help.
The first device to use Choueiri’s equation was the Jambox, now one of the biggest sellers at Apple stores. This wireless speaker delivers lo-fi 3D sound but only if you sit in the ‘sweet spot’. Move around, jiggle your head, and it’s lost.
As the pair of OMA Mini speakers in his living room suggests, Choueiri wouldn’t be happy with that. Fidelity aside, it’s one thing to sit still, concert hall-style and listen but who does that in real life? We work, walk, get up, lie down or, at the very least, turn our heads, while we listen.
So he began to work on a way to create 3D sound capable of following the listener around a room. Now, remember the pinna? Choueiri also worked on customising the sound to individual ears. The latter proved easier than the former but after more tinkering, the BACCH was born.
A computer-controlled algorithm, the BACCH reproduces 3D sound tailored to an individual ear. It also includes an infra-red tracking camera and an adapted version of Phase Erase, a British technology in which speakers working in concert create directional beams of sound that can be steered electronically. This enabled the doctor to extend the ‘sweet spot’ across an entire room. And tailor it to several people at the same time.
“So now,” he smiles “each person gets two beams of sound as well as their own filter. As they move around, the camera tracks their heads and directs the speakers to make multiple, moving sweet spots. It works beautifully.”
And so, I discover after lunch, it does. As I sit transfixed and envious in front of those Minis, Choueiri starts to calibrate a filter for me. The BACCH box, all 54,000 USD of it, sits mutely beside the amplifier. It has few features, the hard work of turning is all done via a dedicated iPad.
He plays a couple of sounds, tones really and taps away. Five minutes later, he declares it’s ready. I hand back my earphones, which are used in the tuning process and he selects the first track.
As the orchestra begins to play – I think it’s Bach – I close my eyes. The sound is stunning but that’s expected. One doesn’t hook USD 12,000 speakers up to any old boombox. But then the clarinets kick in. I’m able to pinpoint each and every one of them spatially. My mouth drops. It’s not just that the violins are to my centre left but that behind them, I can hear the harpsichord and in front of them, I can hear the violins. The sections are so precisely located, I feel like I could get up and walk between them.
The next piece, also orchestral, is even more dramatic. The recording has been made on-stage because I can hear instruments in front of me, to either side of me and then suddenly, as the cello sounds, directly behind me. I shiver. Memories of that misspent youth flood in. Then, the music was in my head, piped in on headphones. Listening through the BACCH, it’s in my head again. But freed of the earphones, it’s as though my head’s the size of Choueiri’s living room.
He takes me through the paces. Classical morphs into Jazz, Jazz into Rock, Rock into Choral, Choral into Classical Arabic. I turn my head, lean left, then right, the camera tracks me and the sound follows. There isn’t a moment when the spell is broken.
An hour later, I’m certain that if I had that USD 54,000 on me, I’d be busily pressing it into Choueiri’s hands. I can’t imagine listening to music again without one. As solutions go, this one seems pretty ultimate.
“Maybe someone will come up with another solution that’s more practical,” the doctor says, as he walks me out. I cast one last envious glance at the BACCH. “The one thing you learn from the last 30 years is that technology tends to win when it’s portable and practical. I won’t be leaving my day job yet.”
PHOTOGRAPH: FranK Wojciechowski