Another, maybe better solution: use a NodeMCU or WeMOS development board instead of the Nano + ESP-01. Those boards connect directly to the USB as well. I do assume the piezo sensor can work on 3.3V.
NodeMCU is very convenient for development, not necessarily "better". After all it also has an ESP8266 on board, but with all the extras like regulator, USB/TTL interface, and even circuitry to make the ADC go all the way from 0-3.3V.I'm using NodeMCU boards for development but finished projects get the bare bones ESP8266 with only the external components it needs. Much smaller.