Assessing the role of spectral and intensity cues in spectral ripple detection and discrimination in cochlear-implant users
Spectral modulation transfer functions (SMTFs) for 15 CI subjects. Ripple detection threshold (in dB) for each of seven different spectral ripple frequencies (0.25, 0.5, 0.75, 1.0, 1.5, 2.0, and 3.0 rpo) is depicted.
SMTFs for Clarion-I, Clarion-II, and Nucleus subjects (top, middle, and lower panels, respectively) over an extended range of spectral ripple rates. The dotted horizontal lines correspond to a ripple detection threshold of 30 dB.
Interpolated ripple frequency (in rpo) for ripple detection threshold, or spectral modulation threshold (SMT) = 30 dB, as a function of spectral ripple discrimination threshold (rpo).
RAU scores for sentence recognition (A) and vowel recognition (B) as a function of average SMT for 0.25 and 0.5 rpo. (C), (D) SNR50% for sentences and vowels, respectively, as a function of the average of ripple detection thresholds at 0.25 and 0.5 rpo.
Individual SMTF (ripple detection threshold as a function of spectral ripple frequency) for subject D10. The vertical line indicates the spectral ripple discrimination threshold for this listener.
SMTFs for three normal-hearing subjects. Ripple detection thresholds (in dB) for each of 15 different spectral ripple frequencies (0.25–60 rpo) is displayed. Spectral ripple discrimination thresholds are indicated by vertical lines.
Intensity difference limens (ΔL) for each subject. Error bars represent 1 s.d.
Individual subject and device characteristics. Gender, age when tested, duration of implant use prior to the study, etiology of deafness, duration of bilateral, severe-to-profound hearing loss prior to implantation, implanted device, and sound processing strategy. The processing strategies include Continuous Interleaved Sampling (CIS), Multiple Pulsatile Stimulation (MPS), HiResolution-Paired (HiRes-P) and Sequential (HiRes-S), and Spectral Peak (SPEAK).
Correlations and corresponding p values (with no post-hoc Bonferroni corrections for multiple comparisons) for three summary measures of ripple detection (the average threshold at ripple rates of 0.25 and 0.5 rpo, the average threshold at ripple rates of 2 and 3 rpo, and the interpolated ripple rate at which the threshold peak-to-valley ratio was 30 dB), and speech recognition measures.
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