Short-term study of the effect of speech coding strategy on the auditory performance of pre- and post-lingually...

The auditory performance of cochlear implantees is linked to numerous variables, such as audiological characteristics, age and type of speech coding strategy. In recent years, many different ways of processing sounds have been developed, with possible implications for auditory performance. The purpose of this study was to evaluate the intra-individual differences of patients for speech perception tasks in quiet and in noise as a result of switching from a standard strategy [Continuous Interleaved Sampling (CIS)/Simultaneous Analog Strategy (SAS)] to Hi-Resolution (HiRes).

A total of 14 post-lingual adults implanted with the Clarion CII were selected for trials. At switch-on, six patients chose a CIS strategy and eight an SAS strategy. After an average period of 9.3 months, all patients were switched over to HiRes. All patients were tested (open-set mode) with bisyllabic words and sentences, in both quiet and noise [speech/noise ratio (SNR) = +10]. Testing was carried out after an initial period with the CIS/SAS strategy and 3 months after switching over to HiRes.

After switch-over a significant improvement was seen for both speech in quiet (words +25.2%, sentences +10.8%) and speech in noise (words 44.8%, sentences 45.4%).

Despite individual differences, all patients improved their performance with HiRes use, the greatest improvements being seen under unfavourable listening conditions (SNR = +10). Subjective improvements in speech discrimination and overall sound quality perception were reported even after the first week of HiRes use.