Very interesting thread. I am just beginning to look into either arduino or Raspberry Pi to recognize not bird calls, but the distinct rapping noise a woodpecker makes while making holes in our redwood cornerboards. The noise is very loud and has been described as: "For example, Downy Woodpeckers hit the substrate about 16-17 times per second, and a drumming event can last 0.25-1.8 seconds. (Ritchison) from Drumming, Tapping and Drilling by Woodpeckers - why, when, deterring. I am hoping that such a distinctive waveform should be much easier to identify than speech or bird calls, so I won't need to do FFTs or have a huge library to compare inputs against. Any advice will be appreciated.