A randomized, double-blind, cross-over trial of two speech coding strategies in cochlear implantation

Cochlear implantation is the primary therapy for profound deafness. A cochlear
implant provides hearing by direct electrical stimulation of the auditory
nerve. The translation from the acoustic sound, recorded by the implant*s
microphone, to the electrical stimulus for the nerve is called the speech
coding strategy. Current implant technology provides an impressive improvement
of auditory function. However, one of the main limitations is a severe diffulty
understanding speech in noise. In addition, the current implants are not able
to transmit intonation in speech or melody in music. The ENT clinic in
Groningen has developed a new speech coding strategy: phase-lock speech (PLS)
coding. This strategy distinguishes itself from existing strategies by the
explicit coding of acoustic fine-structure. A previous pilot study (METc
reference 2008/167) suggested that PLS may lead to better speech understanding
in noisy listening situations than an existing state-of-the-art strategy. In
addition, PLS may improve the perception of pitch and melody.

Hypothesis: PLS will improve speech understanding in noise in comparison to
HiRes, an exisiting state-of-the-art speech coding strategy. The objective is
to test this hypothesis. A secondary hypothesis is that PLS improves pitch
perception. A secondary outcome of the study is a proof of the secondary
hypothesis.

A randomized, double-blind, cross-over trial of two speech coding strategies

Intervention: A cochlear implant functions in conjunction with a dedicated
external hearing aid, that is usually referred to as the speech processor.
Subjects wear a body-worn speech processor during two study terms, each 3 weeks
long. The processor replaces their usual behind-the-ear processor. During one
term, the PLS is used. During the other term, HiRes is used. Hearing function
is tested before the term start, and at the end of each term by audiometric
testing and a questionnaire. The terms are separated by a period of 1 to 2
months, during which the subjects use their usual behind the ear processor.

Burden: During each of the two study terms, the subjects use a body worn
processor. This processor can be worn e.g. on the belt, and connects to the
implant via a wire and a standard head piece. It is less convenient than their
usual clinical behind-the-ear processor. Each term involves three visits to the
ENT-department of the UMCG: Day 1: for initial fitting of HiRES or PLS and
questionnaire, duration: 1.5 hour, Day 8: second fitting session for fine
tuning of HiRes or PLS. Day 21: audiometric assessment, completing
quessionaire, duration 2.5 hour.
Risk: There is no known risk associated with participation.
Benefit: There is no direct benefit for the participatiors. The study is
intended to test a technique from which subjects may profit in the future.