code: def rayleigh_spectrum(self, fftlength=None, overlap=None):
          
          return spectral.psd(
              self,
              spectral.rayleigh,
              fftlength=fftlength,
              overlap=overlap,
          )
docs: Calculate the Rayleigh `FrequencySeries` for this `TimeSeries`.
  
          The Rayleigh statistic is calculated as the ratio of the standard
          deviation and the mean of a number of periodograms.
  
          Parameters
          ----------
          fftlength : `float`
              number of seconds in single FFT, defaults to a single FFT
              covering the full duration
  
          overlap : `float`, optional
              number of seconds of overlap between FFTs, defaults to that of
              the relevant method.
  
          Returns
          -------
          psd :  `~gwpy.frequencyseries.FrequencySeries`
              a data series containing the PSD.