Do the 5.1 Stereo Headphones Really Work?

Tamor asks: "Zalman, the company behind some extremely high quality PC noise-reducing products are now selling real 5.1 surround sound headphones. The surround effect is achieved by placing 3 drivers in each ear-piece. As a geek-with-young-family this product's pushing all the right buttons for me, it looks cool, and means I can finally achieve surround sound without waking the kids. Or does it? I was sure that to place a sound spatially your brain relies on the delay between hearing the sound in one ear and then the other. If your left ear only hears the left 3 channels, and your right ear only hears the right 3 channels isn't this making it more difficult for spatial placement to happen? Do you know if/how these are achieving surround effect if each ear is only hearing half of the audio field?"

Comments

Re:Physics Problem

[Otter]

There was a famous neuroethology experiment with barn owls. They have asymmetrical ruffs on their ears, one pointing up and one down. Sounds have a different volume in each ear depending on the altitude of the source.

But, it was also showed (by putting headphones on them, playing a mouse sound and watching how their heads moved) that they use volume to determine altitude and time offset to determine bearing. So it's definitely possible -- although I have no idea what system human perception uses for the same problem.

Spatialization can work with headphones

[esm]

Sorry, I have no experience with these headphones. But: about 10 years ago, I volunteered as a test subject for some experiments done at NASA Ames (Mountain View, CA, USA). One of them was for a device called the Convolvotron. It's a thingy (sorry for the technical term) which takes multiple sound sources and "localizes" each one so it sounds like it's coming from a different place. It worked incredibly well with only two speakers. The big problem was distinguishing between straight-in-front and straight-behind. With headphones and human ears, I suspect that's just a darn difficult problem. But side-front, side, and side-rear were very easy to differentiate.

Although the tests took place in a sound chamber, they were kind enough to give me a demo tape -- and this tape is amazing. They demo about 5 different voices (simultaneous ATC conversations), both flat and spatialized. Flat, it's impossible to differentiate them. With the convolvotron, it was possible and easy to track each conversation separately. Each one sounded like it came from a different place.

This was early 90s. Processing power has certainly increased since then. It should be possible, and relatively cheap, for someone to use Convolvotron-like technology to convert a 5.1-channel signal to spatialized L-and-R ones for use with regular headphones. There shouldn't be a need for special headphones.

Lots of Google hits for "Convolvotron". Enjoy.

cues

[ballpoint]

Left-right stereo has been here a long time and it works wonders with headphones. No doubt about that.

And since any sound arrives at your two cochleas, it must be possible to simulate any sound position just by exciting your two ears, preferably with in-ear phones.

But I have a hinch that cues about whether a sound is at the back or front come subconsciously from:

1. Turning your head and registering the changes in sound.
2. Echoes and reverb. This only works if you know and 'feel' the room. (*)
3. Changes in frequency response due to the structure of your ears. This only works for sounds you know.

As the headphones are fixed to your head the first, and probably the most important, cue disappears. The room where the sounds were recorded does not match the room you're in, so the second cue disappears. And finally you will be listening to new, unknown sounds. There goes the third cue as well.

But in true /. fashion, I'm posting this without actually having experienced 5.1 headphones with more than one speaker on each side. I'd like to try though.

(*) While I'm listening with isolating in-ear buds, it is strange that the sound changes dramatically the moment I enter a building from the outside. Hard to explain by reverb and echo as there is little sound leakage from the buds to the outside and vice-versa.