new_contents: """
  spectrogram
  =======================
  
  
  """
  ###########################################################
  # Context
  # ----------
  
  ##############################################
  # Example
  # --------
  #
  # In the following example, we compute and plot a spectrogram
  # from a signal emitted by a dolphin to see the time-frequency components
  #
  from spectrum import Spectrogram, dolphin_filename, readwav
  data, samplerate = readwav(dolphin_filename)
  
  p = Spectrogram(data, ws=128, W=4096, sampling=samplerate)
  p.periodogram()
  p.plot()
  
  
subject: add an example