The Knowles Corporation have extended their range of surface mount MEMs (micro-electro-mechanical system) microphones to include a new model sensitive to ultrasonic frequencies. The company anticipate that the SPH0641LU4H-1 sensor will play an important role in the development of gesture control systems used for smartphones, tablets and other mobile devices.
The microphone has a frequency response extending to 80 kHz to allow finger tracking and the 3D resolution of finger and hand gestures. The microphone module includes a preamp and measures just 3.50 x 2.65 x 0.98 mm making it small enough to use multiple units around the screen edges. A minimum of three are necessary to triangulate finger position but more will improve resolution. The microphone is also sensitive to audio frequencies showing a flat response up to 20 kHz and a signal-to-noise ratio of 64.3 dB(A).
Ultrasonic signals can also be used to transmit data between handheld devices and accurately track special ultrasonic-sensitive styluses. This new ultrasonic microphone is said to consume three-times less power than other digital microphones. It has an "always on" voice-activated (235microAmp) low-power mode when not in use and can quickly power up when needed. Sensitivity is matched between units by plus or minus 1 dB. Mass production of the new ultrasonic microphones will begin in the third quarter of 2014.