Introduction:
The development of small speech processors for cochlear implants is a great challenge for manufacturers, as – due to the transcutaneous wireless signal and power transmission – the power consumption of cochlear implant systems is inherently high. Subsequently, the battery occupies a significant amount of space inside the external speech processor.
For many years, Cochlear uses 900 Hz/channel as their default stimulation rate, although data from older publications suggest that also lower rates could be used without sacrificing hearing performance. However, the data was not yet conclusive, so a new study investigating the effect of stimulation rate on speech understanding as well as frequency discrimination was initiated. Frequency discrimination is an important aspect, as lower stimulation rates might hamper the perception of rate pitch, i.e. the perception of the fundamental frequency of different talkers in so called cocktail party scenarios.
Method:
The study consists of an active and a passive branch. In the active part, rates of 1200 Hz and 500 Hz are being compared with regard to frequency discrimination and modulation detection below 500 Hz. In the chronic part, rates of 900 Hz and 500 Hz are compared to each other. Here, speech tests (Monosyllables and Oldenburg Sentence Test) as well as frequency discrimination will be examined at 900 Hz first and subjects will be sent home with a 500 Hz stimulation rate. At the the next appointment, the test battery will be repeated at 500 Hz.
Results:
Current data indicated similar hearing performance at the different stimulation rates.
Conclusion:
Lower stimulation rates in the range of 500 Hz seem to be applicable in the clinical routine.
