ANF FTCs obtained by a tracking algorithm along with the ANFs’ average firing rates obtained subsequently during rate-level function acquisition. The firing rates are represented by the size of the black dots and are shown here as a second method of verifying the thresholds detected by the tracking algorithm. ANF G237u5: CF = 6.34 kHz; spontaneous rate = 5.9 spikes/s, rate-level function step size = 10 dB SPL. ANF G319u8: CF = 8.30 kHz, spontaneous rate = 1.8 spikes/s, rate-level function step size = 5 dB SPL. ANF G254u7, CF = 4.48 kHz, spontaneous rate = 0.5 spikes/s, rate-level function step size = 10 dB SPL.