Acoustical differences between sound categories. a) Red, blue and green lines show the average power spectrum of their respective sound categories (see legend). Stars highlight frequency bands showing a significant effect of sound category. 95% confidence intervals are indicated by shaded areas. b) Time-frequency analysis. The significance of the sound categorical difference effect is indicated by the colormap. Black areas indicate non-significant results. Frequency axis as in figure 1a. c) Power Analysis in time. Red, blue and green lines show the average power of the respective sound categories over the 200 ms duration. Black stars indicate time points showing a significant effect of sound category; blue and green stars indicate significant post-hoc tests. Note that the largest effect of sound category is a higher power in the low frequencies for voices and environmental sounds compared to bird songs.