Background: Adults with cochlear implants (CIs) are usually implanted unilaterally. To preserve
binaural advantages, a noninvasive method involves maintaining the hearing aid (HA)
on the contralateral ear; the choice of HA for this purpose is therefore crucial.
In recent years, the use of frequency transposition has gained a renewed interest
in clinical practice. This type of processing records information from the high-frequency
region and conveys it to a low-frequency region where there is still some residual
hearing.
Purpose: To conduct an investigation and examine whether adults with unilateral CI derive
benefits from a HA utilizing linear frequency transposition (LFT) on the contralateral
ear.
Research Design: A two-period, single-blind, repeated-measures crossover design was conducted to examine
the combination of LFT in conjunction with a CI. Speech recognition tests were performed
in quiet and in noise with LFT either activated or deactivated. The Speech, Spatial
and Qualities of Hearing Questionnaire (SSQ) was used to measure subjective benefit.
Study Sample: The participants were nine frequent bimodal users, five males and four females, with
a moderate to profound high-frequency sensorineural hearing loss in the nonimplanted
ear.
Intervention: The current study was conducted using the Widex Mind440 power (m4-19) behind-the-ear
HA. The participants acted as their own control in a total of seven conditions: (1)
bimodal with own HA, (2) CI only, (3) own HA alone, (4) bimodal new HA LFT-off, (5)
new HA LFT-off, (6) bimodal new HA LFT-on, and (7) new HA LFT-on.
Data Collection and Analysis: Monosyllabic words in quiet and the Swedish version of Hearing in Noise Test (HINT)
were used as speech test materials. Stimuli were presented in sound field at a speech
level of 65 dB sound pressure level (SPL) via a loudspeaker at a distance of 1 m from
the participant in a sound-treated room. The SSQ was administered in each session
evaluating the three bimodal conditions. SPSS software was used for statistical analyses.
General linear model (GLM) analysis of variance for repeated measures was performed
and followed with Bonferroni-adjusted post hoc pairwise comparisons.
Results: Participants performed better with CI only than with HA alone, and the bimodal conditions
were superior to the CI alone. No significant differences (p > .05) were observed when comparing the LFT-on with LFT-off regardless of whether
the use of CI was included in the different listening conditions in objective and
subjective measurements.
Conclusions: The results suggest an advantage for CI patients with a HA in the opposite ear, and
that the LFT neither degraded nor enhanced speech performance in conjunction with
a CI in quiet or in noise in comparison to when it was deactivated.
Key Words
Binaural hearing - bimodal stimulation - cochlear implant - hearing aid - linear frequency
transposition - speech recognition
