Frequency shifts of KIC 3733735 calculated using 180-day subseries shifted every 60 days.The points obtained from independent spectra are shown as full black circles. The power spectrum is centred at a ν_max = 1950 μHz with a range of ±300 μHz and a smoothing of 31 points. The mean spectra used as the reference for the cross-correlation are generated with independent spectra. The pink curve is the S_ph computed by Mathur et al. (2014a). The pink triangles are the integration of the S_ph to the same 180-d ranges as the frequency shifts.