Oh, I hate to set you off onto this quest, but to make that an effective imager, you need two things to make your life easier. A precise means to move it along the Z axis, perhaps up to two meters or more, and a local "coherent" reference sound. Zone plates and Gas Balls also come to mind, but more as test sources rather then as lenses.
Virtual TDOA by scanning the data off SD cards needs too much processing power. Adding the local coherent reference, allows the microphone diaphragm to become a mixer and phase detector.
I used to work for a company that had world records in directivity and intensity of sound. That lasted a year.. I had started on a similar scanner, but done with far less elements. You really only need a sparse array if you have some control over what your imaging.
When I worked for the company that did CT imaging, I had to learn that for certain modalities of imaging, it was best to realize that each image involved exactly the same series of software processing steps, and rather then use a general purpose computer, small arrays of FPGAs were used.
In the past just boards full of TTL were used, mimicking certain processor instructions on a parallel, repetitive, basis. On a modern CT machine, 6 Gigabytes per second of data were coming off the sensor down four fibers in parallel, no single processor made could handle that pipe. FYI, the A/D converters for all 512 by 64 sensors were all current to frequency converters, which is the easy way to break the A to D barrier without buying massive arrays of flash AD converters. Its very easy to measure period over six orders of magnitude using an inverse counting scheme with some interpolation...
I might upload something tomorrow, if I can find the book in the piling system. Your on to something very useful, and you don't know it yet. I cant find a good copy of Winston E. Kock's images on line, but I have a feeling you'll improve upon them. Dr. Kock's method used photo film as an integrator and storage medium. He imaged both near field sound and microwaves using a swinging arm, a neon lamp, and a detector. It looks like garbage until you add a local phase reference. These days that reference could be a noise sequence as well, but um, getting busted for ITAR scares me some times.
Steve