So if I replace my 1 MOhm resistor with, say, a 2 MOhm resistor I will increase its sensitivity (double?).
Will that also protect the Arduino better or the higher the parallel resistor the more the need for the 100 KOhm resistor in series?
And, on a related topic, if a piezo is not ideal for detecting, actually measuring, breath velocity, what other sensor would you recommend?
Do you mean detecting a person breathing lightly, or a blowing hard through a tube?