Spectrograms, spectra, and temporal envelopes of the acoustic stimuli. A–C, Spectrograms (A), spectra (B), and temporal envelopes (C) of the four original whistles used in this study. D–F, From left to right: spectrograms (D), spectra (E), and temporal envelopes (F) of the four vocoded whistles using 38, 20, and 10 frequency bands. G–I, From left to right: spectrograms (G), spectra (H), and temporal envelopes (I) of the four original whistles embedded in a vocalization-shaped stationary noise at three SNRs (+10, 0, and −10 dB).