Figure 4.

Schematic representation of the spectrogram of the isolated fundamental frequency of two descending phrases, a DP2 and a DP3 (a). The sound spectrogram displays time (seconds) on the x-axis, frequency (Hz) on the vertical axis. We describe acoustic parameter collection of unit duration (in red); intervals (in blue); inter-onset intervals (in green); percentage of time to the minimum (ptmin) and maximum of pitch (ptmax, in purple); maximum and minimum pitch (f₀max and f₀min), fundamental frequency at the beginning and at the end of a unit (f₀start, f₀end, in light blue). In the spectrum (b), the fuchsia dotted line marks the frequency corresponding to the upper limit of the second quartile of energy in the spectrum (Q50). The sound spectrum displays sound pressure level (Spl/dB) on the x-axis, frequency on the vertical axis.