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Piezoelectric MEMS mics soars with 70dB signal-to-noise ratio

Posted: 23 Sep 2014 ?? ?Print Version ?Bookmark and Share

Keywords:MEMs? microphones? Vesper Technology? IoT?

Applications Crowley claims will be made possible by their piezoelectric mic are remote-less TVs that answer to voice commands even when they are blaring football scores. Household appliances that answer to voice commands even in the midst of chaotic family background noises, wearables that take dictation, ultrasonic MEMS stethoscopes and security systems whose cameras only need to be turned on when they hear a suspicious noise and all the IoT devices on the horizon.

Many of these solutions are also being explored with gesture control which often requires video, but audio solutions, on the other hand, require much less power, Vesper claims.

Smartphone makers will almost certainly snap-up Vesper microphones to improve not only voice commands, but dictation, noise cancellation and flawless audio-controlled voice-zooming which focuses on a single source of audio while shooting videos by virtue of multiple mic beam steering.

How it works

Vesper was co-founded in 2009 by CTO Robert Littrell who worked with co-founder, University of Michigan professor Karl Groshbuilt as a Ph.D. student. (The University of Michigan is paid a royalty on each piezoelectric microphone sold.)

Since then, Vesper has built a patent portfolio around their proprietary piezoelectric technology, which works quite differently from a traditional microphone. Instead of a traditional diaphragm, which requires a noise-producing perforated backplate, Vesper's piezoelectric transducer is square and divided into four triangles, in the shape of an "X" drawn between opposite corners, with just enough space between them that they never touch. The piezoelectric material (aluminium nitride) expands and contracts in response to the sound coming in its port producing an ultra-low noise signal. The piezoelectric material is also relatively unaffected humidity and moisture, which causes reduced sensitivity in traditional capacitive MEMS microphones.

Vesper piezoelectric MEMS mic

The piezoelectric MEMS chip is wire bonded to an analogue application specific integrated circuit (ASIC) in a 3.35mm x 2.5mm x 1mm package that is pin-compatible with the best-selling capacitive microphones today. SOURCE: Vesper

Vesper's business model is fashioned after Infineon, which only makes wafers (albeit Vesper's wafers will be made in a MEMS foundry.) However, one of Vesper's investors is the company that will dice its wafers and package them into a standard 3.35mm x 2.5mm x 1mm housings alongside an application specific integrated circuit (ASIC) that amplifies the sound signal and processes it for analogue output (plug compatible with Knowles). Vesper's first model will use a bottom port, but top-port designs are in the making.

It already has its first customer, which is the unnamed company that will dice its wafers and package its microphones and which also has a stake in the Vesper. They already sell MEMS microphones in high-volume to original equipment makers worldwide and will add Vespers piezoelectric microphone to their catalogue.

-R. Colin Johnson
??EE Times

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