What is the most practical application for this technology? Could you use it to pinpoint sounds coming from a car like a squeak?
A similar technique is very popular in industrial automation to spot leaks in compressed air pipes and their connections from far away. These leaks are extremely loud in the ultrasonic range. It's overlayed with a camera picture.
That's ultra expensive gear.
I’ll guess «ultra expensive» partly due to very low volumes made for a customer that can afford a lot.
I've always wanted this for videoconferencing room. A microphone array around the screen should be able to dynamically focus on the active talkers and cancel out background noise and echos to get much better sound quality that the muddy crap we usually get.
If there were a speaker array around the screens too, you might be able to localize the audio for each person so that it seems like the sound is coming from where their head is on the screen.
Beamforming is standard in modern conference room gear. It's being used for making a video focus on the active speaker and optimizing his audio.
Have a look at the "Meeting Owl" for example.
It works great up to a limit (around 5m) then you will need additional microphones closer to the speaker.
Shure sells a variety of array microphones (and the software) that handles similar things. I've never used one, but heh.
Microsoft Research had papers on speaker arrays that allowed speaker focus and noise cancelling a couple of decades ago. I think the technology eventually ended up in the Kinect.
I think Cisco had something similar in their large screen meeting room video conferencing systems that could do positional audio tracking of multiple people. Could be wrong, but I think that was at least 10 years or so ago, if not more.
You just need to buy actual video conferencing gear, this is par for the course.
I wish could rent one to figure out which device in my office has a squealing capacitor. I can hear it well enough to be driven crazy by it, but not well enough to find it. I start disconnecting things to narrow it down but then convince myself that it's my ears ringing.
I'm unsure if I'll age out of this problem, or if worse hearing will just recreate it at different thresholds.
You might have some luck with a spectrum analyzer app[1]. A fixed-pitch whine should show up as a line on the waterfall graph. If you move the phone around to differently locations, you might see the line getting stronger or weaker. You can also try rotating the phone to different orientations to see if it is coming from a particular direction.
I used this to locate an annoying squeal coming from some equipment at work once. And to confirm that it wasn't imaginary.
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[1] On Android, I like these two:
Spectroid (https://play.google.com/store/apps/details?id=org.intoorbit....). If you use this, consider turning on the waterfall display in the settings.
Spectral Audio Analyzer (https://play.google.com/store/apps/details?id=radonsoft.net....). This has more color options for the waterfall display.
Phyphox is a great sensor suite app for undergrad Physics experiments, and it includes a spectrum analyzer. Also, it supports both iOS and Android.
The tech is beamforming .. the applications are AV conferencing, camera tracking, voice lift, or sound reinforcement