Princeton professor invents a sound system that plays music in 3D

Edgar Choueiri's invention cuts out crosstalk

PUBLISHED : Friday, 07 November, 2014, 10:43am
UPDATED : Saturday, 08 November, 2014, 11:52pm

Music lovers are always looking for ways to enhance their listening experience, and Lam Wai-shan is no exception. The 40-year-old technology entrepreneur heard about a Princeton University professor who had developed a 3D sound system, and two years ago had the chance to experience it for himself.

Lam and his wife were visiting Princeton, in the US, where they met Professor Edgar Choueiri, director of the engineering physics programme and chief scientist of the university's laboratory for advanced spacecraft propulsion. Choueiri may be a rocket scientist, but he's also a diehard audiophile, who has worked on the system for 12 years.

Lam was curious to try a demonstration of the cutting-edge sound system, called BACCH - band-assembled crosstalk cancellation hierarchy - and the scheduled two-hour visit stretched into eight hours, including lunch and a home visit with the Lebanese academic.

"After that I couldn't sleep - it was either jet lag or adrenaline, but in that whole week afterwards I only got a few hours of sleep," he recalls. So Lam ordered his own BACCH system and flew Choueiri to town to calibrate and customise his computer. A year later, Lam received his BACCH-SP - SP stands for "stereo purifier" - and can now enjoy music that literally surrounds him.

"BACCH can change an audiophile's life," says Lam, who made the innovative system available in Hong Kong in September. "It busts many myths. The experience is so dramatic and obvious that it's the correct way to listen to stereo. I had to have it at home."

For a demo in his North Point office, I enter a grey room and sit in a black leather chair in the middle. In front of me is a grey curtain with no speakers in sight. Lam sits next to me and instructs me to close my eyes. Using an iPad, he begins to play music. The sounds literally fill the room.

One minute, a guitar duet is seemingly performing right in front of me. Then there are voices singing a madrigal; next, sounds from a Paris train station with the whistle of a train, people speaking in French, and the sound of footsteps.

Then I hear record producer and composer David Chesky saying: "I'm in a church now 30 feet from you ... now I'm 15 feet ... and now I'm whispering in your right ear."

He really was. I couldn't help but laugh out loud. How can this be - in a room that is practically an acoustic dead zone? It defies audiophiles' belief that reverb is needed to enhance sound quality. Another misconception is that most speakers should be placed 2.4 metres to three metres apart. BACCH speakers in his demo are less than 1.5 metres apart.

So just how does the system work? For a start, it's far more advanced and effective than surround sound, which works "when there are a large number of people, like in a movie theatre", Lam explains.

"That's when the sound 'flies' away from you and only works where there are speakers positioned around the room. But BACCH only uses two speakers, directly in front of you, yet you can hear someone whispering in your ear. The trick is in the playback."

Lam explains there are three factors in hearing: the inter-aural time difference, or the time the sound takes to arrive in one ear compared to the other which helps the brain analyse where the sound is coming from; and inter-aural level difference, or the volume of the sound which is slightly louder for one ear than the other. The last factor is the tonality of the sound you hear, which is dependent on the shape of one's outer ears.

When listening to typical sound systems, the sound that is meant for the right ear can also be heard in the left ear, and vice versa, making it difficult for the brain to differentiate where the sound is coming from (unless you're wearing headphones). This is called crosstalk - where there is a form of interference that confuses the brain.

"Without cancelling crosstalk, your brain doesn't get the information it needs to hear in 3D," Choueiri explains in an introductory video on YouTube. But by creating a "wall", the sounds meant for the left ear don't reach the right ear, and vice versa.

"The filter substantially reduces crosstalk and it brings you back to normal, natural hearing," Lam says.

This explains why measurements, particularly of your head, the width of your ears and even your torso, are important factors in establishing the "invisible wall" between the left and right ears for optimum settings for your BACCH sound system.

As a result, the machine placed right in front of you helps to restore how you naturally hear things - how a bird is singing on a tree above us to the right, or how the car is approaching us on the left. Lam says that although BACCH is primarily produced for one listener, others can enjoy the experience as long as they are positioned in a line, but not side by side.

The BACCH system's speakers are hardly large boxes and, in fact, look like screens that are semi-transparent, which Lam says makes the sound more focused.

All kinds of music can be played through BACCH, ideally acoustic, but it also works well with live classical and jazz music, natural ambience sounds and Pink Floyd.

The effect works with most stereo recordings, although a small number of recordings have been made especially for the BACCH system. When music is recorded for BACCH, there are only two microphones, which are placed inside a dummy's head - the listener - who sits before the musicians. In some cases they are placed apart from each other to clarify exactly where they are in the room.

The system can also be applied in 3D television and movies. "The images are great but the sound is lousy. At best it's surround and it doesn't give you a sense of depth," he says.

His technology can also be used for teleconference meetings so that people can clearly tell where the voices are coming from, and also improve the quality of hearing aids.

While there are a small number of converts who have heard about BACCH through word of mouth, there are others who are in denial.

"This is shocking to some people. I had a client who has been trying to improve his sound system for 40 years in his flat in Central," Lam says.

"I invited him here to try out this sound system, and afterwards he couldn't accept it. He couldn't believe that this was all he needed."

So far he has sold more than a dozen of the BACCH-SP to clients in Australia, Japan, Hong Kong and Beijing.