(Color online) Illustration of the distortions introduced by incoherent operation. Note that the Hilbert envelope of a signal does not represent any specific tone component in the original signal.
(Color online) The extracted CIS envelopes and HSSE modulators for the “eas” segment of “easy” in quiet and in noise under four-channel condition. The spectrogram of the “eas” segment is displayed on the left. The waveform in the second row represents an IEEE sentence saying “it's easy to tell the depth of a well,” for which the estimated F 0 contour is displayed in the first row. The speaker's pitch is about 230 Hz.
(Color online) Acoustic simulation schemes of HSSE (A) and CIS (B), with the total number of channels being N. In (A), the multiplications between band signals and complex exponential functions (e.g., ) represent frequency downshift operations; the block means taking the real part of a complex signal.
The mean intra-subject performance on HINT (a) and IEEE (b) sentence recognition tests with CIS (hatched bars) and HSSE (filled bars) vocoders. The SNR was fixed at 5 dB across all masking conditions. Error bars represent the standard error of the mean.
(Color online) The estimated F 0 profile of the female (dashed lines) and the male (solid lines) speaker in pronouncing jī, jí, jĭ, and jì, respectively. The F 0 variation amount for each tone is displayed along with the F 0 profile. ST stands for semitone.
(a) The average intra-subject performance on Mandarin tone identification with CIS (hatched bars) and HSSE (filled bars) vocoders. (b)–(e) Subjects’ mean score on recognizing flat, rising, falling then rising, and falling tones, respectively. Error bars represent the standard error of the mean.
Simultated neural discharge patterns under CIS (A) and HSSE stimulation (B), respectively. Within (A) and (B), the top row shows the electric encoding of stimulus jĭ by a CIS/HSSE processor for one electrode; the bottom displays the raster-plot of the evoked neural spike train. The regions labeled ROIs 1–3 will be sampled in the analysis of interspike intervals.
Histograms of interspike intervals. Panels (A)–(D) correspond to stimulus jī, jí, jĭ, and jì, respectively. Within each panel, the histograms on the left were sampled from a CIS-evoked spike train and those on the right were from an HSSE-evoked spike train. From top to bottom, the sample regions are sequentially ROIs 1–3. Vertical dashed lines indicate histogram peaks; only ISIs longer than 2 ms were considered in locating the peaks, because the stimuli's F 0 is below 500 Hz.
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