docs: def fundamental_frequency(s,FS):
      # TODO: review fundamental frequency to guarantee that f0 exists 
      # suggestion peak level should be bigger 
      # TODO: explain code
      """Compute fundamental frequency along the specified axes.
  
      Parameters
      ----------
      s: ndarray
          input from which fundamental frequency is computed.
      FS: int
          sampling frequency    
      Returns
      -------
      f0: int
         its integer multiple best explain the content of the signal spectrum.
      """
      
      s = s - mean(s)
      f, fs = plotfft(s, FS, doplot=False)
      
      #fs = smooth(fs, 50.0)
    
      fs = fs[1:int(len(fs) / 2)]
      f = f[1:int(len(f) / 2)]
      
      cond = find(f > 0.5)[0]
      
      bp = bigPeaks(fs[cond:], 0)
      
      if bp==[]:
          f0=0
      else:
          
          bp = bp + cond
          
          f0 = f[min(bp)]
      
      return f0