Pop corn timer

  After burning countless bags of pop corn in the microwave, i thought that there must be a better method of timing the cooking time.
  A microphone would be placed in the microwave. During the first minute or so of operation, the microphone would pick up the ambient noise and set this as a base line. It could then pick up the sound of the pop corn popping.
  When the frequency of the popping decreases to one every two or three seconds, the microwave would stop.