Do you want the "volume level" or the sampled peaks of the output going to the speakers? Volume is simple, you've already found the code for it. Sampling the output is a whole other story. Now you have to consider getting the output of 1 to 8 speakers. This sampling can occur very fast, but can your serial port implementation keep up with the rate of data you want to transmit? How fast are you looking at sending data out the serial port? You might want to look at this[^] link for a sample on MSDN. RageInTheMachine9532