Earlier quoted context omitted.
The audio from the 60fps video sounds pretty bad though, which I suspect is mostly because of inherent maths/physics limitations rather than anything that software can improve. Edit: They mention capturing frequencies up to five times higher than the 60Hz frame rate, which would mean a maximum frequency of 300Hz, which would suggest the equivalent of 0.6kHz audio, which is a 73.5th of the audio rate of a CD. I doubt…
There is some small possibility of improvement through software techniques, such as maybe data assimilation, which can use information from surrounding time-frames to improve the measurement. This is assuming that the magnitude of vibrations changes a lot slower than the vibrations themselves, which is usually true, and how most audio compression works. It may be able to clean up the sound a little. However, I would…
Suppose the camera scans 720 lines in HD every 1/60 second. Each row is offset in time by 1/43200 second. A rigid object could be slightly offset in space on each line of pixels, indicating that sound waves perturbed it in the time gap between when the camera captured each line. So that subframe video data can be turned back into audio at a much higher frequency than that apparent 60 Hz video sampling rate.
In other words, we're not just talking about 60 frames-per-second from a camera. It's really perhaps 43,200 rows per second, an enormously higher sampling frequency.