I had saved on my computer some time ago a blog site that had directions on how to make a sound trigger that could be built that would fire a camera's shutter during high speed photography projects. I can't seem to find and would like to try making something like this. There's a guy on here that has some photos of balloons exploding. If you are reading this, please indicate how you are firing your flash. Thanks!
I made a sound trigger way back in the early 70's. It was done with a coffee can and a rubber membrane and contacts attached to the center of the membrane. Sound moved the contacts and fired the flash. It was pretty tricky to get set just right but it did work. The balloon shots you refer to above was done with luck. Dark room plus remote trigger when you think the dart is going to hit the balloon.
“Amateurs worry about equipment, professionals worry about money, masters worry about light, I just make pictures… ” ~ Vernon Trent