Supplement Number 1

We present an alternative to figure 1 in the main manuscript. Namely, to facilitate the comparison of both representations, the Fourier transform is now shown in logarithmic scale in figures \ref{fig:fig1log}C,D,G,H. By comparing figure 1 in the main text and supplementary figure 1, it is clear that the logarithmic scale is disadvantageous to the short-time Fourier transform, which is obtained with linear frequency resolution.