Graeme Clark Collection

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Author: Seligman, Peter × End date: 1999 × Start date: 1990 × Type: Conference Paper ×

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    Direct current measurements in cochlear implants: an in vivo and in vitro study
    Huang, Christie Q. ; Carter, Paul M. ; Shepherd, Robert K. ; Seligman, Peter M. ; Tabor, Bruce ; Clark, Graeme M. ( 1998)
    Direct current (DC) was measured both in vivo and in vitro in cochlear implant electrodes with stimulation at moderate to high pulse rates in monopolar and bipolar modes. In vivo DC was approximately 2-3 times higher than that measured in vitro. In vivo DC levels were <100 nA even at very high rates, although DC levels increased as a function of stimulus rate and charge intensity. DC levels were lower: in the monopolar than in the bipolar stimulation condition. Stimulation with a monopolar capacitively coupled extracochlear electrode showed even lower DC levels in the intracochlear .electrodes. Our results indicated that the Nucleus electrode shorting system is able to maintain a low level of DC during very high rate stimulation for both monopolar and bipolar modes.
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    An extension of the Multipeak speech processing strategy for the MSP/MINI 22 cochlear implant system
    Jones, P. A. ; McDermott, H. J. ; Sellgman, P. M. ; Millar, J. B. ( 1992)
    The speech perception of three post-linguistically deaf adults using the Nucleus MSP/Mini System 22 cochlear implant system programmed with a new speech processing strategy, MPEAK+AO. was evaluated. The MPEAK+AO strategy retains all the information of the standard Multipeak speech processing strategy and additionally presents acoustic components below 400Hz to the most-apical electrode. This extra spectral Information may help implantees understand speech, particularly in noise. Since the estimated fundamental frequency is presented as the rate of stimulation at a fixed intracochlear site and is thereby potentially perceived more easily. and the amplitude of the stimulation on the apical electrode, associated with the voice fundamental, Is directly determined from the estimated energy in the relevant spectral region. these coding factors may provide a better representation ot the prosodic information in speech and a more complete auditory feedback signal. The comparison between Multipeak and MPEAK+AO included tests of vowel, consonant and CNC word recognition. Speech materials were presented with both a male and female speaker. Sentence material. presented with background masking noise (four-speaker babble) was also used. The results showed that the new strategy significantly improved the ability of these MSP users to recognise words in open-set sentences in noisy conditions.
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    Preliminary results with a miniature speech processor for the 22-electrode Melbourne/Cochlear hearing prosthesis
    Dowell, Richard C. ; Whitford, Lesley A. ; Seligman, Peter M. ; Franz, Burkhard K.-H. G. ; Clark, Graeme M. (Kugler & Ghedini, 1990)
    The 22-electrode cochlear prosthesis developed by the University of Melbourne in conjunction with Cochlear Pty Ltd has been used successfully by profoundly deaf patients since 1982 and is now a part of everyday life for some 2000 people in many countries around the world. The implanted part of the prosthesis has remained relatively unchanged in this time except for the alteration of the design in 1986 to incorporate an implanted magnet and reduce the overall thickness of the device. The implanted magnet eliminated the need for wire headsets which were difficult to fit and in some cases did not maintain the position of the external transmitter coil adequately. This was felt to be essential before the prosthesis could be used in young children.