Hu, Hongmei and Hartog, Laura and Kollmeier, Birger and Ewert, Stephan D.
(2022)
Spectral and binaural loudness summation of equally loud narrowband signals in single-sided-deafness and bilateral cochlear implant users.
Frontiers in neuroscience, 16.
pp. 1-18.
ISSN 1662-453X
Abstract
Recent studies on loudness perception of binaural broadband signals in
hearing impaired listeners found large individual differences, suggesting the
use of such signals in hearing aid fitting. Likewise, clinical cochlear implant
(CI) fitting with narrowband/single-electrode signals might cause suboptimal
loudness perception in bilateral and bimodal CI listeners. Here spectral
and binaural loudness summation in normal hearing (NH) listeners, bilateral
CI (biCI) users, and unilateral CI (uCI) users with normal hearing in the
unaided ear was investigated to assess the relevance of binaural/bilateral
fitting in CI users. To compare the three groups, categorical loudness
scaling was performed for an equal categorical loudness noise (ECLN)
consisting of the sum of six spectrally separated third-octave noises at equal
loudness. The acoustical ECLN procedure was adapted to an equivalent
procedure in the electrical domain using direct stimulation. To ensure the
same broadband loudness in binaural measurements with simultaneous
electrical and acoustical stimulation, a modified binaural ECLN was introduced
and cross validated with self-adjusted loudness in a loudness balancing
experiment. Results showed a higher (spectral) loudness summation of the
six equally loud narrowband signals in the ECLN in CI compared to NH.
Binaural loudness summation was found for all three listener groups (NH,
uCI, and biCI). No increased binaural loudness summation could be found
for the current uCI and biCI listeners compared to the NH group. In uCI
loudness balancing between narrowband signals and single electrodes did
not automatically result in a balanced loudness perception across ears,
emphasizing the importance of binaural/bilateral fitting.
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