I am a developer who recently got bugged by Audio processing / Digital Signal Processing. Putting it to use I was able to make a small whistle detection program

I am a developer who recently got bugged by Audio processing / Digital Signal Processing. Putting it to use I was able to make a small whistle detection program[1]. I need to know how can I improve this program or better say, a primer on advance aspects of Audio analysis. [1]: http://shubhamjain.github.io/whistlerr/ http://shubhamjain.github.io/whistlerr/