The current study used the self-fitting algorithm to allow listeners to self-adjust hearing-aid gain or compression parameters to select gain for speech understanding in a variety of quiet and noise conditions. Thirty listeners with mild to moderate sensorineural hearing loss adjusted gain parameters in quiet and in several types of noise. Outcomes from self-adjusted gain and audiologist-fit gain indicated consistent within-subject performance but a great deal of between-subject variability. Gain selection did not strongly affect intelligibility within the range of signal-to-noise ratios tested. Implications from the findings are that individual listeners have consistent preferences for gain and may prefer gain configurations that differ greatly from National Acoustic Laboratories-based prescriptions in quiet and in noise.
Normal-hearing (NH) listeners maintain robust speech understanding in modulated noise by "glimpsing" portions of speech from a partially masked waveform-a phenomenon known as masking release (MR). Cochlear implant (CI) users, however, generally lack such resiliency. In previous studies, temporal masking of speech by noise occurred randomly, obscuring to what degree MR is attributable to the temporal overlap of speech and masker. In the present study, masker conditions were constructed to either promote (þMR) or suppress (ÀMR) masking release by controlling the degree of temporal overlap. Sentence recognition was measured in 14 CI subjects and 22 young-adult NH subjects. Normal-hearing subjects showed large amounts of masking release in the þMR condition and a marked difference between þMR and ÀMR conditions. In contrast, CI subjects demonstrated less effect of MR overall, and some displayed modulation interference as reflected by poorer performance in modulated maskers. These results suggest that the poor performance of typical CI users in noise might be accounted for by factors that extend beyond peripheral masking, such as reduced segmental boundaries between syllables or words. Encouragingly, the best CI users tested here could take advantage of masker fluctuations to better segregate the speech from the background.
This study looked at different methods to preserve interaural level difference (ILD) cues for bilateral cochlear implant (BiCI) recipients. One possible distortion to ILD is from automatic gain control (AGC). Localization accuracy of BiCI recipients using default versus increased AGC threshold and linked AGCs versus independent AGCs was examined. In addition, speech reception in noise was assessed using linked versus independent AGCs and enabling and disabling Autosensitivity™ Control. Subjective information via a diary and questionnaire was also collected about maps with linked and independent AGCs during a take-home experience. Localization accuracy improved in the increased AGC threshold and the linked AGCs conditions. Increasing the AGC threshold resulted in a 4° improvement in root mean square error averaged across all speaker locations. Using linked AGCs, BiCI participants experienced an 8° improvement for all speaker locations and a 19° improvement at the speaker location most affected by the AGC. Speech reception threshold in noise improved by an average of 2.5 dB when using linked AGCs versus independent AGCs. In addition, the effect of linked AGCs on speech in noise was compared with that of Autosensitivity™ Control. The Speech, Spatial, and Qualities of Hearing Scale-12 question comparative survey showed an improvement when using maps with linked AGCs. These findings support the hypothesis that ILD cues may be preserved by increasing the AGC threshold or linking AGCs.
Self-adjustment of hearing aid gain can provide valuable information about the
gain preferences of individual listeners, but these preferences are not well
understood. Listeners with mild-to-moderate hearing loss used self-adjustment to
select amplification gain and compression parameters in real time on a portable
touch screen device while listening in quiet and noisy backgrounds. Adjustments
to gain prescribed by the National Acoustics Laboratories' non-linear fitting
procedure (NAL-NL2) showed large between-subject variability. Known listener
characteristics (age, gender, hearing thresholds, hearing aid experience,
acceptable noise level, and external ear characteristics) and listener
engagement with the self-adjustment software were examined as potential
predictors of this variability. Neither listener characteristics nor time spent
adjusting gain were robust predictors of gain change from NAL-NL2. Listeners
with less than 2 years of hearing aid experience and who also had better hearing
thresholds tended to select less gain, relative to NAL-NL2, than experienced
hearing aid users who had poorer thresholds. Listener factors explained no more
than 10% of the between-subject variance in deviation from NAL-NL2, suggesting
that modifying prescriptive fitting formulae based on the factors examined here
would be unlikely to result in amplification parameters that are similar to
user-customized settings. Self-adjustment typically took less than 3 min,
indicating that listeners could use comparable technology without a substantial
time commitment.
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