recognize unwanted sounds, noises, and deleting them algorithm
Provided that the noise is uniform across your sound and that you have regions where only noise is present, you can make use of a technique called spectral subtraction. The whole process consist of 4 steps. 


  
  Find a noise-only region and apply an FFT on it in order to obtain the noise profile (noise spectrum). The longer the noise region, the better the noise profile (resolution) you'll get (use longer FFT lengths)
  Apply FFT on your entire sound. This way, you'll get the spectrum for both the signal (people talking) as well as the noise.
  Subtract the noise profile from the overall sound spectrum (2-1). Ideally, you'll end up with the signal-only spectrum (of course, some
  noise will still remain).
  Perform an inverse FFT on the signal spectrum obtained in step #3 to get a time-domain signal (waveform) .
  


If the filtered signal still has some unwanted artifacts, you may try to interpolate the signal spectrum prior to performing the IFFT (step 4)

Note that you don't have to break up your signal into smaller chunks (this is not STFT)