code: def convolve_filter(signal, impulse_response):
      
      if impulse_response is not None:
          # print 'interpolated calibration'#, self.calibration_frequencies
          adjusted_signal = fftconvolve(signal, impulse_response)
          adjusted_signal = adjusted_signal[
                            len(impulse_response) / 2:len(adjusted_signal) - len(impulse_response) / 2 + 1]
          return adjusted_signal
      else:
          return signal
docs: Convovle the two input signals, if impulse_response is None,
      returns the unaltered signal