(Color online) Magnitude spectra of FFRs averaged across six subjects with FFRs for the two polarities added (dashed line) or subtracted (solid line). Panels (a) and (b) show the FFR spectra for a frequency-shifted complex tone, presented at 75 dB SPL, for which harmonics 2+3+4 of a 300-Hz F0 were shifted down by 56 Hz in the absence and presence of a narrowband noise (140–440 Hz, presented at 85 dB SPL), respectively. Panels (c) and (d) are as (a) and (b), but with the harmonics shifted up by 56 Hz and a noise in the range of 160–460 Hz. Panels (e) and (f) show the FFR spectra for a 244-Hz 75-dB SPL pure tone in the absence and presence, respectively, of a narrowband noise (84–404 Hz) presented at 90 dB SPL.