One sharp frequency change. A: A time series with a sharp change in frequency half way through the observed time frame, simulated from d(t) = sin(ωt) with ω1 = 0.2 rad/s and ω2 = 0.4 rad/s. B: The posterior probability distribution for the estimated frequency using a local BSA, BSAL, with a window size of 10, which is one third of the number of data points in a period of the first frequency. Nevertheless, the resulting distribution is so narrow that it resembles a sharp line. C: The wavelet power spectrum using a Morlet mother wavelet , with a lower cut-off at ω = 0.1 rad/s in the spectrum. D: The STFT power spectrum, window size of 100 and overlap of 5. Both the wavelet and STFT results gives the correct answer but with high variance.