3D sound steering and the audible enclave

Now you hear it, now you don't. Behold the power of bendy beams!

- Carrie Marshall

Wouldn’t it be great if you could get AirPods-style personal audio without having to stick anything either in or on your ears? A team of researchers at Penn State University in the US are trying to do just that. They've created a way to focus sound so that you can hear it perfectly - but the person next to you won't hear a thing. Their version of the technology creates what's called an ‘audible enclave’, which is a small pocket of sound. If you're in the right place you'll hear the audio as intended. But if you move even slightly you won't hear anything.

The Penn State project is using a dramatic version of what's also known as sound steering, beam steering or beamforming. And it could be coming to public places near you, and maybe one day your HomePod too.

What is sound steering?

With stereo sound, such as from your hi-fi or a pair of HomePods, slightly different signals are sent from each speaker to your ears - so you might have the lead guitar louder in the left speaker, and maybe a keyboard in the right. That makes your brain think that the guitar is over on one side, the keyboard is on the other, and the singer's in the middle.

Sound steering takes that idea, adds more speaker drivers and then uses digital signal processing to very subtly shape the sound coming out of those multiple speakers by adjusting volume, timing and frequencies.

By doing that, it can control how the various speakers’ sound waves interact with each other and with the sound of the room, and it can calculate the specific place or places where the sound waves will combine. That calculation and adjustment enables it to focus sound beams in much the same way you can focus multiple lights to illuminate a single spot or multiple spots.