Mics that record in 3D ambisonics are the next big thing

glitcher | 186 points

Ambisonics is a fascinating technology. It's basically the same concept as differential stereo encoding (where you record an R+L and R-L channel and use them to derive R and L, or just play the R+L channel for mono) extended to all three axis to create surround sound (so you have a sum channel, a horizontal difference channel, a vertical difference channel, and a depth difference channel). This was all developed in the 70s (and thus out of patent today) but abandoned for more direct means of encoding surround since it was more complex to process the signals for not much gain. Of course now with DSPs the signal processing is much easier and with VR there's suddenly a niche for it to fill since it fully preserves the 3D soundscape (unlike e.g. 7.1 surround which only records 7 point sources at fixed positions).

On a side note, the upcoming 1.3 release of the Opus codec is adding support for Ambisonics-encoded surround sound.

MrRadar | 6 years ago

I actually built two of my own 1st-order ambisonic mics and the decoder plugins about 6 years ago. I shelved the project since I couldn't (and still cannot) afford a playback system beyond stereo :(

It was pretty cool to rotate the soundfield through headphone playback to have the recorded audio whizzing around your head :)

I never thought at the time that VR would become popular again and provide a good use case for this technique.

wdfx | 6 years ago

Audio professional here. Ambisonic recording is great, though it does have limitations because you're baking in spatial information in a way that will limit editing later - it's not a magic bullet for location audio, although it will be a valuable supplement.

If you're interested in getting into this, you can feel good about the Zoom product. They deliver outstanding value for money. I've used them on several feature films, first as backup recorders but later as the primary audio capture platform.

anigbrowl | 6 years ago

Marvel's new Wolverine podcast/radio play is recorded in ambisonic sound [1] if anyone wants an easily accessible example.

Per the article:

The ambisonic mic necessitated a different method of recording the show. Instead of the standard “one-person, one-mic” studio approach that the actors recorded simultaneously, in the same room. The approach allowed for more interaction between actors, more like staging a play than recording an audiobook.

1 - https://www.theverge.com/2018/5/30/17409704/wolverine-the-lo...

michaelbuckbee | 6 years ago

I wonder how people play back those 3D recorded sounds?

If you want a 3D audio experience, it's possible to do that with just two microphones and a dummy head model [1]. Then you just play back the recording with earbuds. It's pretty fascinating that something so simple works, but you can only listen from the position where the recording was taken.

I guess if you record using one of those complicated mic arrays, it may be possible to simulate the effect of your pinnae in software, allowing you to move around in a virtual environment, and hear the 3D audio from different points?

[1]: https://en.m.wikipedia.org/wiki/Dummy_head_recording

jakobegger | 6 years ago

Ambisonic recording is cool, but audio technology in general is full of technobabble and pseudoscience, so I wonder how theoretically grounded these systems are.

Are these companies actually understanding the science and producing well-calibrated systems that can accurately record and reproduce pressure waves in 3D? Or are they just taking a bunch of microphones and gluing them in an aesthetically interesting arrangement, and then playing them back in an ad-hoc way?

modeless | 6 years ago

Back in grad school our professor [Tom Holman](https://en.wikipedia.org/wiki/Tomlinson_Holman) did some amazing work in spatial sound, specifically for cinema. He chose to double the number of channels from 5.1 to 10.2 and the results were pretty amazing.

If my memory is working correctly, the channels chosen were Left, Left-Center, Center, Right-Center, Right, High-Left, High-Right, Left Surround, Right Surround, Back surround, and two low frequency channels. His research indicated that the human ear has better vertical localization towards the front (potentially having evolved to detect tree-dwelling predators, for example), and experiments with dummy head recording produced inadequate results for theatrical reproduction.

Sadly it doesn't seem to have caught on (yet), probably due to the expense of having to retrofit cinemas. Anyway, it was really cool to listen to. I imagine the use of ambisonic recording rigs will greatly benefit the 360° video playback experience. Don't know what the other use cases might be yet.

philrw | 6 years ago

I have been trying to get professional musicians interested in ambisonics for about 20 years, since I first learnt about it from my brother and I haven't yet found a single one who is at all interested in experimenting with it.

I have had a few going as far as denying that ambisonics could even have any kind of useful application in music at all.

The visual arts crowd seem far less dismissive, weirdly.

cuboidGoat | 6 years ago

They are not hard to diy, 4 electret capsules like Primo EM184. But by the time you've built the holder and preamps, might as well spend $300 on the Zoom H3-VR.

I don't think they have much use outside VR - you basically need head tracking for headphone use (or a lot of speakers)

dharma1 | 6 years ago

I’m just starting to learn the process of capturing and mixing 360 sound. I’m confused though, is the “only” benefit of buying an ambisonic mic just have to do with the ease of workflow? Sort of how it’s best to use a matched stereo pair for stereo recordings if you want the best result with the least hassle?

umairadil | 6 years ago

What do you all think of Creative Technology's "Super X-Fi"?

http://www.mobilitytechzone.com/lte/news/2018/09/05/8812379....

yoyobo | 6 years ago

I'm wondering if someone can clear up a related question. I've always heard that two ears are needed to identify the direction of sound. However, I can tell the direction of a sound when one ear is covered up and without moving my head. Try it yourself: put a TV or other sound source behind yourself, positioned a little to the left or right, cover one ear, and you'll see that you can reliably tell whether it's more left or more right. So I think that something more complicated is going on within the ear and that a single ear is not strictly unidirectional.

mysterypie | 6 years ago

If you like to see a full talk about this topic, held by a renowned German microphone company "Schoeps Mikrofone", watch this video: https://youtu.be/K-ktLM0dQeA

This high-end manufacturer might have a divergent perspective on those topics in comparison to some other companies. Still, they supply recent high budget productions in 3d audio, film or 3d audio sports events.

hdhacker | 6 years ago
[deleted]
| 6 years ago

Will this be a big thing in ASMR?

Kiro | 6 years ago

Something I don't often hear mentioned is auditory surveillance. An array of highly sensitive 3D microphones with sophisticated processing seems like it could completely destroy most remaining privacy that we have.

shkkmo | 6 years ago

My intuition says that this idea, miniaturized to the size of an atom, might bring back some heretofore unknown information about the atomic realm. Like an atomic, multi-directional sound (or any wave in the EM spectrum) transducer, and then bring that data to higher levels... Yes, I know I'm crazy... <g>

peter_d_sherman | 6 years ago

I wonder whether these types of microphones are suitable for field recording.

peatfreak | 6 years ago

It would be really cool to have music composed for 3D recording.

legionof7 | 6 years ago

This is not mathematically necessary at all. This just reads like astroturfing for an overpriced mic retailer.

tahw | 6 years ago