1. Take any mobile phone with sound editing app.
2. Go to known distance away from target. Like 6 feet in my case.
3. Set mobile to record sound.
5. stop recording.
6. You will see THIS:
That spike is the sound of impact. But is it all that is?
Zoom in. Keep zooming in until you...
I have not as yet tried this out, so I don't know how well it works, but I saw this on an airgun forum, and the reviews are mixed.
There is an Android app that allows your Android device to act as a chrony. It uses sound as a trigger to measure projectile speed in FPS or MPS.
It's called Chrono...
Can you tell me what speedometer Joerg Sprave is using to measure the speed of his slingshots?
Here is a video where he uses his speedometer: