FIG. 6.
Recovered envelopes were observed at low CFs in chinchilla AN-fiber responses to speech fine-structure chimaeras. Neural cross-correlation coefficients (ρTFS, A; ρENV, B) quantify the similarity between single-fiber spike-train responses to a speech token (“A boy fell from the window”) and the corresponding chimaera with fine structure from speech and envelope from a spectrally matched noise. Closed circles: chimaera generated with one analysis band; open triangles: 16-band chimaera. Dashed lines at ρ = 0.1 represent the estimated noise floor for uncorrelated conditions (see Fig. 3). Overall speech level was chosen to be in the upper one third of each fiber’s dynamic range for the original speech token, and ranged from 62 to 72 dB SPL.