Electret Microphone

Using Arduino Audio
8

arduino IDE has an File / Example / 03 Analog / Smoothing. study how it works.
Than find this line:

  // read from the sensor:  
  readings[index] = analogRead(inputPin);

and change it to:

  // read from the sensor:  
  readings[index] =  (analogRead(inputPin) - 136);
  readings[index] = readings[index] * readings[index];

136 - is a value you are reading in silence