A mathematical model that explains the sounds created by knuckle cracking

V. Chandran Suja and A. I. Barakat, writing for Nature Scientific Reports:

The articular release of the metacarpophalangeal joint produces a typical cracking sound, resulting in what is commonly referred to as the cracking of knuckles. Despite over sixty years of research, the source of the knuckle cracking sound continues to be debated due to inconclusive experimental evidence as a result of limitations in the temporal resolution of non-invasive physiological imaging techniques. To support the available experimental data and shed light onto the source of the cracking sound, we have developed a mathematical model of the events leading to the generation of the sound. The model resolves the dynamics of a collapsing cavitation bubble in the synovial fluid inside a metacarpophalangeal joint during an articular release.

I understand less than half of the article, but I'm quite fascinated because: (1) I cannot make make this kind of sound, and (2) There are scientists who spend time and resources to think about these problems.