Profoundly deaf people can often not be helped anymore with
conventional hearing aids that amplify the sound. Most of these
people can be given a sensation of hearing with a Cochlear implant
in which the auditory nerve is stimulated directly by electrodes
shifted into the cochlea. In a Cochlear’s Nucleus Freedom System,
a speech processor analyzes the sound captured by a microphone.
Philips Applied Technologies developed an ultra low power, flexible,
digital speech processor. Based on the speech processor’s analysis, the
electrodes in the cochlea deliver pulses of larger or smaller intensity.
Small hearing aid batteries power Cochlear devices. This requires very low
power consumption. On the other hand new stimulation algorithms and sound
preprocessing algorithms are more computational intensive than the older ones.
Digital speech processor
The digital speech processor is made in a standard Philips CMOS18 process.
To save power the supply voltage is reduced as much as possible, as the power
consumption reduces with the square of the power supply. The supply voltage
can be scaled with an on-chip DC/DC converter. This influences of course the
maximum frequency that can be obtained. To ensure a good performance a library
characterized at low supply voltage has been used for synthesis. Furthermore,
special care has been taken at the design. Several Digital Signal Processors have
been put on the device to ensure a large enough computing capacity.
Philips Applied Technologies won the Medical Design Excellence Award 2006 for its
role as supplier of Cochlear.
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