Overview of the signals selected to build the stimuli for the listening test. For the specific sounds, the figures are based on the raw signal, i.e. before correcting for atmospheric attenuation and removing occasional tonal components. In the upper figures, the absolute amplitudes are arbitrary. In the lower figures, the darker the color, the higher the magnitude. Upper left: power spectrum density (PSD) for the different specific sounds and the residual sound. Upper right: detail of the PSD of raw S1 showing tonal components around 4 kHz. Lower left: sonogram of S1 where clear “swish” could be heard. Lower right: sonogram of R0 where the transients above 1 kHz are bird vocalizations.