The SiSonic sensor from Ruf North America (www.ruf-electronics.com) is only 2.5 mm2 and comprised of a silicon microphone and IC on a micromachined silicon chip. It was developed for use in smart air bag detection, parking assistance, fuel-level measurement, and voice recognition, and has a frequency response of 10-50 kHz and a sensitivity of 20 mV/Pa. In addition, the company offers a line of rotary and linear position sensors. Products include throttle, pedal, EGR, and steering angle sensors and memory mirror and fuel-level sensors.