Wow, check out this cool sound trigger circuit DIY for High Speed Photography!
The general use is quite simple: setup a noisy event to trigger the flash. Since I am using the Sigma EF-500 Flash, which have an internal “dumb slave”, I activate a led to tell the flash when to fire. A more general solution can be found here.
he circuit consists of 2 parts. The first part is a very simple microphone pre-amplifier. The second is the light generator, to trig the Flash.