Not exactly. A sonar maps a surface using sound, while my camera looks at the sound itself.

Think laser rangefinder on a scanner platform vs a camera.

Have you seen light field photography [1]? It would seem that your array is quite similar in concept. I'd imagine that getting images similar to those produced by various SONAR imaging technologies is a similar sort of deconvolution problem. If you're looking for textbooks or scientific papers to review, I think the field of tomography is also ripe with methods to explore here.

I'd challenge the notion however that this isn't 'just' a passive SONAR device. Keeping the camera analogy, active SONAR use spread spectrum pings, much like the white light of a camera's flash. Your camera lacks a flash function, and its lens is maybe not yet as in focus as it could be.

If you did want to add a flash, you're likely a $0.02 piezo device and maybe $20 in other various parts (and heaps of numerical processing on a PC) away from having the ability to produce a nice 3D reconstruction of the physical scene.

If you get direct data capture going, please do post some raw data online. I'm sure others would have heaps of fun playing around with it.

1: http://graphics.stanford.edu/projects/lightfield/

Hm, why not - here is the raw data (after PDM decoding) for the 16x16 video from the article: http://orbides.org/etc/snd_16x16_raw.tar.gz (4 Mb)

One file per cell, 16bit integer samples. Stored row by row, 128 slices per frame.

Not sure where to post it, however - here it would be buried.

There ARE sonars that deliver an image.

http://blueprintsubsea.com/starfish/images/sonar/452/sf452_s...

That's just one example - look for side scan sonars for the earliest stuff (https://en.wikipedia.org/wiki/Side-scan_sonar) or sonar imaging for the latest stuff (http://www.tritech.co.uk/product/gemini-720i-300m-multibeam-...)

Such systems are ubiquitous on commercial fishing vessels.

https://en.wikipedia.org/wiki/Fishfinder

No. SONAR sends out an ultrasonic ping and times the response of its echo to get a distance.

This project is similar in that it involves visualization from audio, but apart from that, it's quite difference. This is the ability to see a sound. To derive the positions of arbitrary sounds in a viewing plane, and render it like you would a picture or video.

Yes. Passive sonar only listens to the noise. Passive sonar systems are often arrays too. So the analogy holds quite well from a distance ;)

https://en.wikipedia.org/wiki/Sonar#Passive_sonar

He's still driving the scene - illuminating it, if you would.

No.

Most sonar is active (sends out pings) and has only one input (one microphone)

It builds pictures by directing the ping and measuring time until the response.

This is fundamentally different than an array of microphones passively listening to, and creating a fine grained picture of some sound source.

> Most sonar is active (sends out pings) and has only one input (one microphone)

While I believe the US Navy doesn't prefer the term "Passive Sonar", submarines and some surface ships are equipped with hydrophone arrays (either on the hull, or towed arrays, or both) as well as active sonar; this isn't an uncommon thing. (I was under the impression that the active sonar didn't use a single hydrophone, but instead used the same hydrophone array used for passive detection.)

Yes it is. Despite all the other replies asserting SONAR is active, passive SONAR systems are very much a thing.

For my undergraduate project years ago I built a microphone array that could be used to locate noisy objects. I demonstrated it by tracking aircraft taking off at a local airport.

Whilst I didn't make 'acoustic photos' with it, I did plot the flight track of the aircraft in real time, and could have a decent crack at identifying it based on frequency content.

Sonar sends out sound and then listens for the echoes though, rather than just take in sound from other sources.

Some types of SONAR send out sound, other types (e.g. [0]) passively listen for sounds and use beamforming to localise the source of the noise.

[0] https://en.wikipedia.org/wiki/Towed_array_sonar