Graeme Clark Collection

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    Loudness summation for two channels of stimulation in cochlear implants: effects of spatial and temporal separation
    McKay, C. M. ; McDermott, H. J. ; Clark, Graeme M. ( 1995)
    An experiment with four implantees with the Mini System 22 device was undertaken to measure the loudness summation across two channels of stimulation, with stimuli in which the current pulses were delivered alternately to each channel. The effects of varying spatial separation, temporal separation, and extent of stimulation were investigated. It was found that the absolute amount of summation varied among subjects, and was in general independent of electrode separation, except for a reduction at zero separation. Widening of the spatial extent of the stimulation did not have a consistent effect. There was a reduction in summation for all subjects at zero electrode separation when the time between the two pulses was increased from less than I millisecond to 2 milliseconds. In conclusion, loudness summation did not appear to be highly dependent on parameters that affect the spatial current spread in the cochlea. Further study of the effect of temporal parameters on loudness may help to quantify interaction between stimulation channels.
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    Musical timbre perception investigated using forward-masking
    Stainsby, Thomas H. ; McDermott, Hugh J. ; McKay, Colette M. ; Clark, Graeme M. ( 1999)
    There is growing general interest in the perception of musical sounds by cochlear implantees. This study was aimed at the perception of one specific aspect of musical timbre, the shape of steady-state frequency spectra. The relationship of the physical and internal spectral shapes was investigated using a forward-masking technique. In addition, the ability of subjects to identify and discriminate selected musical sounds was tested in two related experiments.