massachusetts cochlear implants that restore some hearing to the profoundly deaf have improved steadily over the past two decades although they are called implants however these systems still lie mainly outside the ear researchers hope that one day the entire apparatus which is designed to stimulate the auditory nerves of people who have lost or damaged cells in the cochlea can be implanted in the body but before that goal can be reached cochlear implants will need to use far less power currently the batteries must be changed as often as every four hoursnow a researcher at the massachusetts institute of technology has devised a processor for cochlear implants that he says consumes only about half a milliwatt onetenth of the processing power of current devices such an acoustic processing chip if proven to be effective might be suitable for nextgeneration cochlear devices that are fully implantedthere might be a small bump behind the head said rahul sarpeshkar an associate professor of electrical engineering and computer science at mit who with his group created the lowpower processor but otherwise you wont know from appearance that the person is deafto save power the new processor reverses the traditional pattern for chips used in cochlear implants it does most of the work with analog circuits not digital onesmost people digitize the signal immediately as it comes from the microphone turning the information into bits that a digital signal processor then handles dr sarpeshkar said we did the opposite the signal remains in analog form for most of the processing including filtering the sound and is digitized only at the last interface to drive the control circuitry of the electrodesin the digital age it turns out there are still jobs at which a welldesigned analog circuit can excel yannis tsividis a professor of electrical engineering at columbia university who specializes in merging precision analog and digital circuits on single chips said that dr sarpeshkar had alighted on such an opportunitythe ear does impressive things dr tsividis said but not at high speed it processes information not in the gigahertz range of say a typical intel chip but in the far more leisurely kilohertz rangeanalog circuits can be profitably operated here he said because the design does not demand the high current needed for digital operation the physical world is basically analog he said but at some point chip designers must convert those analog processes to the zeroes and ones of digital design the larger question is when do you do this he asked there is a lot you can gain from doing much of the initial work in analog avoiding the dissipation of power that occurs in digital number crunching where each of millions of elements handles part of the computation that process can quickly empty a batterydr sarpeshkar and his group have been working on the processor project for three