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. 2020 May;147(5):3667.
doi: 10.1121/10.0001304.

Speech masking release in Hybrid cochlear implant users: Roles of spectral and temporal cues in electric-acoustic hearing

Viral D Tejani  1 , Carolyn J Brown  2
Affiliations

Speech masking release in Hybrid cochlear implant users: Roles of spectral and temporal cues in electric-acoustic hearing

Viral D Tejani et al. J Acoust Soc Am. 2020 May.

Abstract

When compared with cochlear implant (CI) users utilizing electric-only (E-Only) stimulation, CI users utilizing electric-acoustic stimulation (EAS) in the implanted ear show improved speech recognition in modulated noise relative to steady-state noise (i.e., speech masking release). It has been hypothesized, but not shown, that masking release is attributed to spectral resolution and temporal fine structure (TFS) provided by acoustic hearing. To address this question, speech masking release, spectral ripple density discrimination thresholds, and fundamental frequency difference limens (f0DLs) were evaluated in the acoustic-only (A-Only), E-Only, and EAS listening modes in EAS CI users. The spectral ripple and f0DL tasks are thought to reflect access to spectral and TFS cues, which could impact speech masking release. Performance in all three measures was poorest when EAS CI users were tested using the E-Only listening mode, with significant improvements in A-Only and EAS listening modes. f0DLs, but not spectral ripple density discrimination thresholds, significantly correlated with speech masking release when assessed in the EAS listening mode. Additionally, speech masking release correlated with AzBio sentence recognition in noise. The correlation between speech masking release and f0DLs likely indicates that TFS cues provided by residual hearing were used to obtain speech masking release, which aided sentence recognition in noise.

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Figures

FIG. 1.
FIG. 1.
(Color online) Postoperative audiograms for the implanted ear and contralateral ear. Open symbols on the right plot represent mean ±1 standard deviation (SD). NR indicates no response. Vertical lines on the right plot indicate the average high-pass cutoff frequency for electrical stimulation and the average low-pass cutoff frequency for acoustic stimulation.
FIG. 2.
FIG. 2.
(Color online) Frequency spectra (left) and time waveforms (right) for spondee and babble stimuli. The spondee spectrum is an average of the frequency magnitude spectra of all 12 spondees. The amplitude of the spondee in the time domain was reduced by 5 dB prior to frequency analysis, reflecting the −5 dB SNR test condition used for this study. The vertical lines indicate the average high-pass cutoff frequency for electrical stimulation and the average low-pass cutoff frequency for acoustic stimulation. Note that in the time waveforms the two-talker babble (top) has a peakier waveform relative to the ten-talker babble (bottom).
FIG. 3.
FIG. 3.
(Color online) Clinical preoperative and postoperative speech recognition outcomes. (Left) CNC word scores in quiet and (right) AzBio sentence scores in noise. Preoperative indicates aided scores in the ear to be implanted. E-Only indicates electric-only. EAS indicates combined electric and acoustic stimulation. Open squares indicate mean ±1 SD.
FIG. 4.
FIG. 4.
(Color online) Spondee recognition in quiet for E-Only, A-Only, and EAS modes. Open squares indicate mean ± 1SD. The dashed line represents chance performance.
FIG. 5.
FIG. 5.
(Color online) Spondee recognition in two-talker vs ten-talker babble for E-Only, A-Only, and EAS modes. Open squares indicate mean ±1 SD. The dashed line represents chance performance.
FIG. 6.
FIG. 6.
(Color online) The masking release and normalized masking release for the E-Only, A-Only, and EAS modes. Open squares indicate mean ± 1SD. The dashed line represents no masking release.
FIG. 7.
FIG. 7.
(Color online) Spectral ripple density discrimination thresholds and f0DL performance for the E-Only, A-Only, and EAS listening modes. The open squares indicate mean ±1 SD.
FIG. 8.
FIG. 8.
(Color online) Correlations between speech masking release and psychophysical performance in the EAS listening mode.
FIG. 9.
FIG. 9.
(Color online) Correlation between AzBio sentence recognition in noise (+5 dB SNR) and speech masking release in the EAS listening mode.
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References

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