user11300: I have an arduino schematic from here  
http://www.arduino-hacks.com/arduino-vu-meter-lm386electret-microphone-condenser/
I have a problem, the output of the circuit (the pin which is going to connect to the analog pin of the Arduino), from what I have measured has 4.5 V (I think it is a bit high). If I print on the serial it gives me something like 827, 826. However when I clap my hands near the microphone or put music on, the data that I get doesn't change a lot (like 1 -2 units). Should I worry about the schematic or about my microphone?
EDIT:
  After I rebuilt the circuit and when playing a song at a medium volume, I get values like this: 419-670. I think it is working, though I would like more opinions about these values (the output voltage is now around 3.20 V).

user3879: The schematic seems to have both inputs of the opamp at 0V (the one connected to the microphone would actually swing a small amount ±). The opamp also seems to be running open loop, with no feedback and would have a very high gain.
This is poor circuit design, ideally the inputs should be biassed at Vcc/2. At best the output would be severely distorted.
I suggest you search for a more suitable circuit. 

11300: <p>I have an arduino schematic from here  </p>

<p><a href="http://www.arduino-hacks.com/arduino-vu-meter-lm386electret-microphone-condenser/" rel="nofollow">http://www.arduino-hacks.com/arduino-vu-meter-lm386electret-microphone-condenser/</a></p>

<p>I have a problem, the output of the circuit (the pin which is going to connect to the analog pin of the Arduino), from what I have measured has 4.5 V (I think it is a bit high). If I print on the serial it gives me something like 827, 826. However when I clap my hands near the microphone or put music on, the data that I get doesn't change a lot (like 1 -2 units). Should I worry about the schematic or about my microphone?</p>

<p>EDIT:
  After I rebuilt the circuit and when playing a song at a medium volume, I get values like this: 419-670. I think it is working, though I would like more opinions about these values (the output voltage is now around 3.20 V).</p>
 3879: <p>The schematic seems to have both inputs of the opamp at 0V (the one connected to the microphone would actually swing a small amount ±). The opamp also seems to be running open loop, with no feedback and would have a very high gain.</p>

<p>This is poor circuit design, ideally the inputs should be biassed at Vcc/2. At best the output would be severely distorted.</p>

<p>I suggest you search for a more suitable circuit. </p>
