Can't I just get a cheap electret microphone, connect it to a pre-amp (for example, this one…http://www.sparkfun.com/products/8872) and then wire the output of that pre-amp to one of the analogue input pins on an arduino and then use the analogueRead() function to decide how noisy it is?Won't this do what I need? Or is it more complicated than that?
Thanks - I understand the need to keep the voltage within the 0-5volt range, but where could a negative voltage come from on the pre-amp circuit?Is not audio a AC voltage with both a positive and negative voltage crossing the common reference? Unless you do something like add a DC offset voltage to a AC voltage there is always a positive and negitive voltage value at any give instance.Good point about sound being logarithmic I forgot that. Cheers