Schlieren photography makes density changes in air visible, so it can show a sound field as a shadow pattern. The problem is that a Schlieren image is a flat projection through the whole field. This build solves that the way a hospital CT scanner does: rotate the subject, take thousands of 2D shots at known angles, and reconstruct a volume from the stack.
The rig is a turntable driven from Python, a Schlieren setup, and an ultrasonic levitator as the subject. The reconstruction runs through medical imaging algorithms and is converted to DICOM, the format radiology software reads. Python scripts, the Schlieren controller code and the 3D print files for the slew bearing and mounts are all published on GitHub.
This is one of the more ambitious amateur acoustics projects of the last year, and the parts list is not exotic. If you already have a turntable and a camera, the gap between this and a normal bench setup is mostly software.