THE MERIT OF USING SILICON FOR THE DEVELOPMENT OF HEARING-AID MICROPHONES AND INTRAOCULAR-PRESSURE SENSORS

An important design rule for a hearing aid is the requirement of a lar ge signal to noise ratio, which is mainly determined by that of the mi crophone and its preamplifier. It will be shown that in order to incre ase the signal to noise ratio it is favourable to integrate the preamp lifier with the microphone, which implies that the microphone should b e made of silicon, preferably with a single wafer technology. For the development of a tonometer for the measurement of intraocular pressure , the application of a silicon force sensor rationalizes that also the flattening of the eye globe is measured with a silicon applanation se nsor, instead of by optical means which is the present practice. A sen sor construction has been developed, which combines a force, pressure and applanation sensor, all made in silicon.