(a,d) Experimental spectrograms, showing transduced mechanical spectra (horizontal axis) versus the optical laser frequency (vertical axis) at two different experimental conditions: (a) cooled at 3 K, incident laser power 20.6 nW; (d) room temperature, 295 K, with incident laser power 124 nW. (b,e) Simulated spectrograms corresponding to those shown in (a,d), obtained by calculating frequency shifts for a large number of motional amplitudes sampled from a thermal distribution, and averaging Lorentzian lineshapes with centre frequencies given by the calculated shifts. The colour bar below panel (e) is shared for all the spectrograms (PSD, power spectral density). (c,f) Individual spectra at various detunings (coloured symbols), overlaid with the corresponding simulated spectrum (solid black lines). Spectra were offset by a factor of 102 between them to avoid overlap.