Sound/noise sensor for Arduino

For quite some time I’ve been looking for some sort of sound or noise sensor. I had some electrolytic microphones lying around, so the only problem was amplifier. 

Well you can choose either some IC or some simple transistor ones. At first I’ve tried LM386, but I found out that it’s not very good. The reason is that this IC is not meant to be used as a pre-amp. I’ve decided to use this single transistor setup with 2N3904. I’ve also bought big white board and drawn the circuit. It’s really cheap sound/noise detecting sensor and it work’s good.

Arduino code :

void setup()

{

 Serial.begin(9600); 

}

void loop()

{

 int minimum = 1024;

 int maximum = 0;

 for(int i=0;i<1000;i++)

 {

  int value = analogRead(A0); 

  minimum = min(minimum, value);

  maximum = max(maximum, value);

 }

 Serial.print("noise=");

 Serial.print(maximum-minimum);

 Serial.println(); 

}