Figure 6.

Functional block diagram of the Advanced Combination Encoder (ACE) sound-processing strategy. A relatively large number of bandpass filters (typically 20) are used to estimate the short-term spectrum of the input signal. The filters have partially overlapping frequency responses covering a wide bandwidth (e.g., 200 Hz–10 kHz). The levels at the outputs of the filters are compared so that only the subset comprising the highest levels is passed to the following stages of processing. The subset typically includes the 10 highest levels, and only the 10 corresponding electrodes in the cochlear implant are activated. The selected signal levels are converted into appropriate current levels of electric stimulation. The digital data transmitted to the implant specify the currents to be delivered by the active electrodes. The resulting stimulation pattern comprises a series of interleaved pulses delivered at a constant overall rate.