ABSTRACT
Perceptual assessment of speech recognition performance with cochlear implants is confronted with problems raised by patients' availability and specificity. These problems can be avoided by using objective evaluation methods based on automatic classification of speech sounds. In the present report, different tuning strategies for the Digisonic cochlear implant were evaluated by discriminant analysis. The results presented here concern the correct classification of vowels. A set of 600 vocalic items, corresponding to 10 vowel categories and produced by 20 French speakers, were processed by the Digisonic DX10 with two different strategies. In the linear strategy, center frequencies of the 15 Digisonic channels were almost equally spaced in acoustic units (Hz). In the mel strategy, center frequencies were almost equally spaced in psychoacoustic units. For each strategy, energy levels of the frequency channels were quantified for each vocalic item and processed by statistical discriminant analysis for classification into 10 vowel categories. Results mainly show that the percent correct classification (PCC) is larger for the mel strategy and that the improvement is due to a higher concentration of frequency channels below 4 kHz. Implications of these results for the tuning of cochlear implants are discussed.
Subject(s)
Cochlear Implants , Deafness/rehabilitation , Phonetics , Speech Perception , Adult , Female , Humans , Male , Speech Reception Threshold TestABSTRACT
For 1973 we have been among the first to claim the multichannel cochlear implant superiority regarding single channel efficacy. However we actually thing that single channel cochlear implant is indispensable in case of total ossified cochlea, and very useful when efficacy/coast ratio must be considered. In order to narrow the gap between multi and single channel device efficacy, we used the new microprocessors possibilities to digitalize the analogic emietter of the single channel system, which we designed in 1987. Owing to a PC keyboard the new emietter allows the speech therapist to select the frequency band width of the input signal, and to determine the threshold level and the dynamic value as a function of six steps values of the stimulus wave frequency. These improvements supply the patient with a better speech intelligibility excepted for vowels discrimination. Comparison of clinical results obtained through the two analogic and digital systems are reported on 4 post lingually and 4 pre lingually deaf patients.
Subject(s)
Cochlear Implants , Signal Processing, Computer-Assisted , Adolescent , Adult , Cochlear Microphonic Potentials , Deafness/rehabilitation , Humans , Speech Discrimination Tests , Speech PerceptionABSTRACT
The hearing aid device is a 4 X 10 X 15 cm box. It is battery operated and monitored by a PC computer. The Texas 320C25 microprocessor performs real-time signal analysis at 16 kHz and gives 16 energy levels ranging from 0 to 8 kHz by Fourier transform. For each frequency band, the energy received is multiplied by a gain determined according to the patient's audiometric characteristics stored in the device's memory. The signal is then synthesized by reverse Fourier transform and sent to the earphone. The performances of this device are discussed and compared with present hearing aid devices.