The overall effect (in particular with regard to this light emission, which really happens – it's not just apparent) is mostly investigated under the name [sonoluminescence](http://en.wikipedia.org/wiki/Sonoluminescence).

Though the process of this luminescence itself remeans unsettled, it is for sure that extremely high temperatures are produced at bubble collapse (in fact, it was conjectured [they might be hot enough to build a nuclear fusion reactor](http://en.wikipedia.org/wiki/Bubble_fusion)!), and this high temperature obviously causes another steam bubble to form very quickly, so that would explain the pulse-oscillation effect.