Piezo mics are pretty cheap, and if wired up to the microphone input of a computer or phone you could probably get better accuracy as well if you used the same

Piezo mics are pretty cheap, and if wired up to the microphone input of a computer or phone you could probably get better accuracy as well if you used the same signal processing techniques. Seems some people have done this already with a PC app: https://timeandtidewatches.com/how-to-make-your-own-timegrapher-watch-education/ https://timeandtidewatches.com/how-to-make-your-own-timegrap...