Binaural spatial enhancement study for cochlear implant users.

A cochlear implant (CI) is a prosthetic device for the inner ear, able to
directly stimulate the auditory nerve. With a CI it is possible to bypass
damaged inner hair cells and provide audible sensations to profoundly deaf
implant recipients. The standard of care in the Netherlands, as well as the UK
and other countries is unilateral implantation. Because detecting the direction
where a sound comes from in the horizontal plane requires two functional ears,
directional hearing is greatly impaired in CI users. If speech comes from the
side, CI users understand speech less well. Speech understanding in noise is
especially challenging for CI users, let alone when the speech comes from the
contralateral side. If there is residual hearing in the contralateral ear, CI
users can wear a hearing aid (HA) in that ear, which aids in speech
understanding in noise. However, the performance of these so-called bimodal
listeners is still very poor in terms of directional hearing, and speech
understanding when speech comes from the HA side.
The company Advanced Bionics (AB) has various clinically used (and CE marked)
speech enhancement strategies available to improve auditory scene analysis.
Beamformers are one of them. They have been used for decades in the hearing aid
industry and have more recently found their way in cochlear implants
(Buechner, Dyballa et al. 2014, Vroegop, Homans et al. 2018). Beamformers are
typically used to create a *beam* in front of the listener where sound passes
unattenuated, and sound (noise) outside the beam is attenuated. This improves
the signal-to-noise ratio and hence improves speech recognition in noise.
Beamformers operate digitally at the input (microphone or front-end) level of
the CI device and change nothing to the inner workings of the cochlear implant
at the auditory nerve level (back-end).
Beamformers can also be pointed to the sides, clinically referred to as
*ZoomControl*. Combining the microphone signals from the CI and HA is called
*StereoZoomTM*. By pointing the beams sideways (*ZoomControl*), speech coming
from the sides can be improved. By combining both signals (*ZoomControl* +
*StereoZoom*) the beams can be focused for more effective signal improvement.

Determine speech understanding in noise with the AB*s bimodal BF directional
hearing technology.

This will be an observational cross-over trial. The total duration of the study
is estimated to be 1 year. It is a cross-over trial as every subject will be
their own control when the speech understanding is tested in CI users, namely
BF technique one and BF technique two switched ON (test) versus OFF (control).
Speech understanding will be tested in 18 study participants.

This study is performed on CI users. The study is considered to involve
negligible risk and minimal burden. Benefits to the CI population at large may
be better speech understanding in noise. Given the small risk and high yield of
this research it is an ethically justified study.