Fig. 5. Fast Fourier transformations (FFTs) of sound stimuli recorded by the hydrophone 2 cm away from the fish (light traces) and the auditory brainstem response (ABR) waves elicited (dark traces). (A) The drumming sound of P. pictus, (B) the two-pulsed sound of B. modesta, (C) the three-pulsed sound of B. modesta and (D) the sound of L. gibbosus. All stimuli and ABRs were recorded at 25 dB above mean hearing threshold of each particular species (30 dB for C). The double-headed arrows in A indicate harmonics of the stimulus that correspond to spectral peaks of the ABRs; the single arrows indicate spectral peaks of the ABR waveforms at frequencies representing additional harmonics of the stimulus. Note the different frequency scalings for each species. The error of the frequency axis is ±20 Hz due to the bandwidth settings of the FFT calculations.

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