Piezo element

Other Hardware Sensors
1

Hello,

I would like to use a piezo element for sound detection.

I found that i need to check the polarity and that i need to put a resistance of 1M in parallel to connect the piezo to an analog arduino port.

  1. Can someone explain why it should be a 1M resistance , i have a 100 K is this not good ?

  2. I have a piezo element from digisound, type S-HRH-V and on this component there is no indication for the polarity ( just 2 black wires ...)
    Piezokeramischer Schallwandler Digisound S-HRH-V online kaufen | Pollin.de

Who can help me out here ?

Thx.