code: def load_psd():
      
      # psd has freq resolution = 1/3 with 6145 samples
      psd = np.loadtxt("ZERO_DET_high_P_PSD.txt")[:,1]
      down_factor = 3
      pad_size = int(np.ceil(float(psd.size)/down_factor)*down_factor - psd.size)
      psd_padded = np.append(psd, np.zeros(pad_size)*np.NaN)
      psd = sp.nanmean(psd_padded.reshape(-1,down_factor), axis=1)
      # now dF = 1
      # length of psd = 2048
      return psd
docs: Resamples advLIGO noise PSD to 4096 Hz