Immersive audio is the new hotness in the recording world. Once upon a time, mono was good enough. Then someone realized humans have two ears, and everyone wanted stereo. For most of us, that’s where it stopped, but audio connoisseurs kept going into increasingly baroque surround-sound setups — ending in Immersive Audio, audio that is meant to fully reproduce the three-dimensional soundscape of the world around us. [DJJules] is one of those audio connoisseurs, and to share the joy of immersive audio recording with the rest of us, he’s developed Maurice, a compact, low-cost immersive microphone.
Maurice is technically speaking, a symmetrical ORTF3D microphone array. OTRF is not a descriptive acronym; it stands for Office de Radiodiffusion Télévision Française, the fine people who developed this type of microphone for stereo use. The typical stereo ORTF setup requires two cardioid microphones and angles them 110 degrees apart at a distance of 17 cm. Maurice arrays four such pairs, all oriented vertically and facing 90 degrees from one another for fully immersive, 8-channel sound. All of those microphones are thus arrayed to capture sound omnidirectionally, and give good separation between the channels for later reproduction. The mountings are all 3D printed, and [DJJules] kindly provides STLs.
Recording eight audio channels simultaneously is not trivial for the uninitiated, but fortunately, [DJJules] includes a how-to in his post. We particularly like his tip to use resistor color coding to identify the XLR cables for different microphone channels. Playback, too, requires special setup and processing. [DJJules] talks about listening on his 7.1.4 stereo setup, which you can find in a companion post. That’s a lot of speakers, as you might imagine.
There are high-end headphones that claim to reproduce an immersive sound field as well, but we can’t help but wonder if you’d miss the “true” experience without head tracking. Even with regular department-store headphones, the demo recordings linked via the Instructable sound great, but that probably just reflects the quality of the individual microphones.
Audio can be a make-or-break addition to VR experiences, so that would seem to be an ideal use case for this sort of technology. Maurice isn’t the only way to get there; we previously focused on [DJJules]’s ambisonic microphone, which is another way to reproduce a soundscape. What do you think, is this “immersive audio” the new frontier of Hi-Fi, or do we call it a stereo for a reason? Discuss in the comments!
This is fantastic, but I can’t help but think that the binaural microphones that are embedded in a pair of simulated ear structures would better reproduce 3D audio.
That was my first thought too. But I think with the described setup you can turn your head during playback and keep the sense of direction.
Binaural audio gives a very good sense of “being there” in 3D space– but only for a fixed head position, and only while wearing headphones. As Manfred says, binaural audio doesn’t hold the illusion very well if you turn your head.
With this technique you can surround yourself with speakers from all directions and everyone in the room gets an accurate reproduction of the soundscape whichever way they face.
I designed the mic for playback on a 7.1.4 system, not headphones. The challenge with binaural is similar to 3D TV’s: not everyone’s eyes or ears are the same dimensions and you need to correct for that. In Binaural it is done with HRTF’s that are custom to each person.
Whose ear structures are simulated?
I assume every human has slightly different ears (kinda like fingerprints) and any virtual/simulated 3D sound via stereo headphones/speakers (HRTF?) lacks that information.
Considering the increasing number of gamers only playing with stereo headphones I think it might be worth studying if HRTF and the like influences their real-world spatial hearing capabilities.
but isn’t simulated HRTF indistinguishable from multi direction mic recordings?
I came in to say similar: How does the multi-mic array data get processed to make the sound appear subject to the head-related transfer function?
The HRTF doesn’t even have to be that good: I made a lot of ambient sound recordings in the 80s with a dual-mic rig with a simple shadow wall between a pair of cardioid mics (no head, no hair, no ear structures). It’s eerie to listen to a recording, hear someone walking up behind you, and turn to see no-one there…
This tutorial doesn’t cover that; the processing section focuses on using the recording with the multi-channel immersive surround system you see in the embedded image.
You can map the 8 channel recording to SPARTA binauralizer plugin in Reaper. It lets you load HRTF’s https://leomccormack.github.io/sparta-site/ With that said, my goal was a far less expensive immersive microphone array intended for playback on 7.1.4 and Atmos systems.
I wonder if the resistor colour coding will actually make sense even to most HAD reader type people in a few years – I know I’ve pretty much never actually used a through hole resistor or seen anything much with them in really. Obviously I still know of them, but for how much longer in this SMD even for most beginner electronic projects world will that be true?
a 12 speaker STEREO setup? What kind of nonsense is that supposed to be?
Or “stereo” in the senses of “boombox”?
WTF are DIN cables(!)? I know the “usual” 5-pinned DIN connectors but dunno what DIN cables are supposed to be.
And DIN isn’t mentioned in any of OPs posts. He’s using XLR connectors (as one would expect today).
It may technically be nonsense, but any home audio setup is referred to as a stereo system in colloquial English, at least the dialect I grew up with.
Yes, DIN was a brain fart. They are indeed XLR. I’ll fix that.
It is so nice that folks still crave stereo sound and this immersive magic. Seems like the new generation is growing up listening to mono sound sources like Bluetooth speakers. Listening to the music in my car, that has a JBL sound system, most music seems to have no stero sound. Then a track from The Doors or Pink Floyd comes on, and I’m there!
Um…
High end headphone setups DO have head tracking…
Or they can. THX has a setup for it that tracks pitch/roll/yaw.
(and you really won’t have the 3 translation DoF without having a VR setup anyway)