Speech Activity Detection- Adhoc Problem with multi source sounds(birds,trees,heavy air) and how to eliminate them completely Here i will first try to put my application agenda


  Typically i am sampling at 8Khz rate and filtering speech components using a BPF(digital)
  now i have got the 0-4Khz components in which essentially &lt;250Hz are not speech so i will eliminate them also
  now i am trying to find out entropy of frame and trying to mark respective frames as voice or non voice if they belong to band 250&lt;=f&lt;=3750 Hz 


so now the problem is while i was doing this at my realtime application side there also non human sounds like birds sound or a ringing of a bell which again fall in to the frequency band i am flagging as speech

so this causes a false alarm of speech even in case of bird sound and bell ringing how to really over come this problem 

what else i can try to do for effectvie speech activity detection
This is not aliasing this is not any phenomenon, there are number of birds whose vocal fall in speech range even a frog vocal falls in speech range so essentially a training based speech detection is required to classify whether a given frame is speech or a non speech 

one such implementation is shown here

Speech Discrimination based on multiscale spectro temporal modulations