Abstract
Previous studies have demonstrated no improved or deteriorated speech intelligibility with the HiResolution Fidelity 120™ speech coding strategy (HiResF120) over the original HiRes strategy. Improved spectral and deteriorated temporal sensitivities have been shown, making it plausible that the beneficial effect in the spectral domain was offset by the worsened temporal sensitivity. We hypothesize that the implementation of fast Fourier transform (FFT) processing, instead of the traditionally used bandpass filters, explains the reduction of temporal sensitivity. In this study, spectral ripple discrimination, temporal modulation detection, and speech intelligibility in noise were assessed in a two-week take-home trial with 3 speech coding strategies: one with conventional bandpass filters (HiRes), one with FFT-based filters (HiRes FFT), and one with FFT-based filters and current steering (HiRes Optima). One participant dropped out due to discomfort with both research programs. The 10 remaining participants performed equally well on all tasks with all three speech coding strategies, implying that FFT processing does not change the ability of CI recipients to discriminate spectral or temporal information or speech understanding.
Highlights
In an attempt to boost cochlear implant (CI) performance, the cochlear implant sound coding strategy “HiResolution Fidelity 120” (Advanced Bionics, Valencia, CA) (HiResF120) was developed [1]
As temporal cues are important for speech intelligibility in noisy environments [19,20,21,22], we hypothesize that the unchanged speech intelligibility in noise is because the beneficial effect in the spectral domain is offset by the reduced temporal sensitivity
The present study examined the effect of fast Fourier transform (FFT)-based filter banks on temporal resolution, spectral resolution, and speech perception in noise
Summary
In an attempt to boost cochlear implant (CI) performance, the cochlear implant sound coding strategy “HiResolution Fidelity 120” (Advanced Bionics, Valencia, CA) (HiResF120) was developed [1]. By simultaneously stimulating 2 adjacent electrode contacts with different weights, the peak of excitation shifts between the 2 contacts, creating an intermediate pitch percept [2,3,4]. This strategy generates up to 120 tonotopic positions, psychophysical data reveal that most CI users are unable to discriminate such small differences in place pitch [4,5,6,7]. As temporal cues are important for speech intelligibility in noisy environments [19,20,21,22], we hypothesize that the unchanged speech intelligibility in noise is because the beneficial effect in the spectral domain is offset by the reduced temporal sensitivity
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