Changes in speech intelligibility as a function of time and signal processing strategy for an Ineraid patient fitted...

To assess changes in speech intelligibility as a function of signal processing strategy and as a function of time for one of the first two Ineraid patients in the United States fitted with a continuous interleaved sampling (CIS) signal processor.

In Experiment 1, the patient was fitted with a CIS processor and measures of speech intelligibility were taken over a period of 4 mo. These data were compared with data collected with the Ineraid. In Experiment 2, three new signal processing strategies were tested. Measures of speech intelligibility were taken at fitting and after a week's use of the processor. In Experiment 3, the number of channels in the processor was reduced to 5, 4, and 3. Each processor was tested at fitting and after a week's use of the processor.

In Experiment 1, immediately on fitting, the CIS processor produced better speech intelligibility for consonants, vowels, and the CID sentences than did the Ineraid. Performance improved over periods ranging from 1 to 4 mo depending on the test material. In Experiment 2, two processors produced significantly better speech intelligibility than did other processors. Most generally, performance dropped slightly when a new processor was fitted and then improved over the course of week. All of the processors produced better speech intelligibility than did the Ineraid. In Experiment 3, five channels allowed similar levels of performance as did six channels. The effect of four and three channels varied as a function of test material. Four CIS channels allowed better performance than did the four analogue channels of the Ineraid.

We conclude 1) that CIS processors can provide much better speech intelligibility than can the analogue processor of the Ineraid; 2) that many CIS strategies, not just one, will produce better speech intelligibility than will the Ineraid; 3) that for this patient, five channels can allow as high a level of word intelligibility as can six channels; 4) that when the number of CIS and analogue channels are equated (at four), the CIS strategy provides better speech intelligibility than does the Ineraid; and 5) that speech intelligibility with CIS processors improves over periods as short as a week and as long as several months after fitting of the processor.