Abstract: An input signal representing speech is preamplified, filtered, and fed foward in parallel to Automatic Gain Control (AGC) circuitry and to a gain controllable amplifier. The AGC detects the peak absolute value of the input signal, charing a capacitor in accordance with such detections. The capacitor is discharged at a faster rate (variable down to 1 msec) when a greater charge value is stored but at a slower rate (variable up to 4 seconds) when a lower charge value is stored. The gain controllable amplifier is controlled for gain inversely to the charge value stored on the capacitor. The AGC captures greater than 60 dB of allowable input signal range, compressing such input signal into a (controllable) limited amplitude dynamic range.

Abstract: An electronic hearing device for stimulating the auditory nerve by way of implanted electrodes wherein sound signals are converted to electrical signals which are divided into separate channels according to their frequencies. The signals of each channel are amplified and applied to the electrodes. The relative amplifications of each channel, after taking into account a threshold amplification, have a ratio of 6 to 7 dB/octave from the channel having the lowest center frequency to the channel having the highest center frequency.