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The science of surround sound: An interview with Arnaud Laborie, Founder of Trinnov Audio

By Marcus Wong - 19 Jun 2018,7:30pm

The science of surround sound

Note: This interview was first published in the March 2018 issue of HWM.

Arnaud Laborie, Founder and CEO of Trinnov Audio.

Living spaces in Singapore are much smaller than what you’re used to. Is that a problem to achieve good audio?

It’s challenging, but possible.

One consideration is the acoustics. The smaller the space, the more complex the acoustics become, so we try to control the acoustics of a space with a microphone and processing. Not only in terms of EQ (where if for example you have too much bass you bring the bass levels down) but really in terms of the time domain.

We've also looked into high spatial resolution By this I mean the ability to localize the sound, so there’s a high degree of precision. For that, we need more than just stereo and even more than 5.1 channels. And so the challenge becomes how to install that many speakers in the room, especially if it’s a small one.

 

Right. That makes me wonder how many speakers you need to actually get proper surround sound.

Ideally the more speakers you add, the greater the resolution you’ll get, and the wider the listening area will be. This also means if you have more speakers, you can have listeners closer to the walls.

I would say start from 7.1-speaker configuration, where you have three speakers near or behind the screen. For high-performance home movie audio, all the speakers should be very close to the screen. Either behind the screen or on the side, and the surround speakers should be on the side or behind you. But we also need to reproduce sound from the top, so adding six up-firing speakers would give you better coverage…

 

That’s a lot of speakers.

Yes, in total I’d say you need sixteen channels for a high-performance home theater. Because if not, the object is not flying over you; it’s flying in front, then it disappears and appears again in the back. Using a 3D speaker layout, it becomes much more realistic because we can reproduce the true nature of sound and how audio travels.

When I’m talking to you in this interview, I’m sitting in front of you, so you hear sound from this direction, and that’s it. But in reality, I’m projecting sound everywhere in the room. Sound goes to the ceiling, to the floor … some sound comes back to you later because of reflections.

Our brains have learned to analyze sound since birth, so you don’t need to see me to know that I’m about one meter away from you. You also have a sense of how big the room is. It’s all this subtle information that makes it realistic.

With today’s surround sound technology we can’t yet reproduce all directions, so we still perceive that it’s a sound reproduction. But with 3D loudspeaker layouts combined with surround sound technology, we can reproduce sound from all directions and create very realistic sound effects.

It’s like the walls disappear, the speakers disappear; and all you hear is sound.

 

Is it possible to make a single sound bar give surround sound like what you might get from multiple speakers?

If you want localization of the sound independent of the speaker positions, then no. Because the speaker position is important. Even with sound remapping technology, the speakers have to surround you. You might have multiple speakers but if you pack them all into one corner of the room, you won’t be able to properly produce sound from the other direction.

It all comes back to the definition of “Sound”.

Sound is wave propagation, so if you have all your speakers in one corner, all the sound waves they produce goes from that corner to you. But if you want to give the impression that the sound is coming from the other direction, you need some wave propagation that comes from behind.

 

Bouncing sounds off walls or ceilings doesn't work as well either?

Well, it can work to some degree, but then it depends on the material of your wall/ceiling. If you have a hard surface, you might be able to get a reasonable result. The problem is that your up-firing speakers need to send audio to the ceiling and only the ceiling; not to you.  And this is a challenge, because any leakage will come to you first.

The brain is very good at analyzing what comes first. And if what comes first is the sound from the speaker and not the ceiling, your brain won’t believe that sound is coming from the ceiling. This is exactly what's happening when you hear some sound from above, but you don’t believe there’s a speaker there.

The speaker will also need to compensate for timing loss too, because your ceiling could be made up of multiple layers, and the first layer reflects only the high frequencies while the second reflects the bass. Your sound bar will need to compensate for that, so it will need to be able to measure all of this and adjust for it to recover the lost frequencies and the time domain for each one. There will also be a lot of absorbance and resonance happening in the room so there will be a lot to compensate for to achieve the effect of a physical speaker.


Read Next: Does Dolby Atmos really bring sound all around?

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