Sound – It’s rocket science

With 3D images astounding half the population and leaving the other half feeling distinctly seasick, it was only a matter of time before another of our senses got the same treatment. Sure enough, 3D sound reproduction is finally with us; but while you might expect Professor Edgar Choueiri, its inventor, to be an audio engineer of some sort, he in fact spends most of his time as professor of mechanical and aerospace engineering at Princeton University. Let the ‘3D sound? It’s not rocket science’ gags commence.

Born in Lebanon and schooled in France, Choueiri now works on spacecraft propulsion in the US, funded by Nasa. But in 2003 a lifelong passion for music led him to wander into a conference of the Audio Engineering Society, where he heard people discussing 3D audio, and why no one had managed to perfect it yet. To Choueiri, this sounded like a challenge.

So he went and did what any good professor would do — read ‘what I think is every paper on the problem’. He soon learnt that any stereo recording (that is, any recording made through separate microphones) — which is almost every recording from the past 60 years — contains enough information to be reproduced in 3D, but, because of sound’s frustrating tendency to spread out from loudspeakers, some of the sound meant for the left ear is picked up by the right ear, and vice versa, destroying the 3D effect. ‘Stereo kind of fell short,’ explains the professor. ‘Imagine watching a 3D movie — if you take off your glasses, the image won’t be in 3D. That’s what happens when you take a good recording and play it through your home stereo — you are seeing without the glasses.’