| 摘要 |
Apparatus for stimulating the cochlea to give a sensation indicative of the pitch of voiced sounds is known and apparatus is described for adding stimulation in response to voiceless sounds. Signals from a microphone passing by way of an amplifier and a bandpass filter 99 reach a zero crossing detector 103, and intervals between successive crossings are measured using counters 104 and 105 and circuits 97, 98, 98', 117, 118 and 118'. Successive intervals found in this way are compared with absolute values in comparators 107, 107' and 108, 108' to determine when successive intervals are comparatively short, indicating voiceless sounds, and comparatively long indicating voiced sounds, respectively. A random noise source 13 is connected to stimulation circuits when voiceless sounds are detected, connection being by way of a switch 113 controlled by logic circuits 110 to 116 and 116', and 119 and 119' from the comparators 107, 107', 108 and 108'. <IMAGE>
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