Vesper has announced their first piezoelectric digital MEMS microphone for audio applications in voice recognition.

Vesper's latest product, the VM3000, is a low-noise digital MEMS microphone that features a PDM output which enables multiplexing of two different microphones on the same data line.

The channel of the microphone (left or right) is enabled with the use of an external pin tied either to VCC or GND and the total pin count of the VM3000 is a mere five.

Thanks to the use of a piezoelectric MEMS element, there is no need for a bias voltage (electret microphones, for example, require a bias voltage). As a result, the VM3000 has an ultra-fast start-up time of less than 200µs. This quick response time enables the VM3000 to capture an entire keyword (such as a wakeup command), and has been demonstrated to be twice as accurate when combined with Vesper’s ZeroPower Listening Technology.

Additionally, the device features the use of a bottom port design wherein the sound entrance to the VM3000 is located underneath, allowing for very compact PCB designs , s well as the simplifying PCB environmental sealing.

The VM3000 and its block diagram. Image from Vesper

Because of the digital nature of the VM3000’s output, the captured audio signal is significantly more immune to RFI and EMI and this robustness is further improved with the use of a metal can design.

The design of the VM3000 also makes it robust to harsh environmental conditions being rated for IP5x for dust conditions and IPx7 for water conditions. To put that into perspective, the VM3000 is able to operate correctly while in dusty conditions as well as water immersion up to 1 meter while still operating. The VM3000 is also resistant to particles as well as being shock-proof making it ideal for even the most demanding environments.

The VM3000. Image courtesy of Vesper

With a supply voltage range of 1.6V ~ 3.6V, a signal to noise ratio of 62 dB(A), a frequency response range of 20Hz to 20kHz, and a current supply of less than 800µA, the VM3000 is an ideal microphone for many applications including beamforming, outdoor applications, wearables, and IP security cameras.

The Growing Utility of Microphones

Vesper has aimed the VM3000 at a series of applications that are inexorably linked to the IoT: "smart speakers, headsets, hearables, TV remote controls, smart home appliances, and smartphones (just to name a few)."

All of these example devices are rather demanding when it comes to microphones, especially given the need for low-power design.

The Internet of Things is really pushing hardware to its limits

Since many IoT devices are mounted in remote locations (or those that cannot be connected to a mains supply), they are often reliant on battery power. Increasingly, these devices are also integrating functionalities such as speech recognition, voice wakeup, and speech commands. Smart home IoT devices such as the Amazon Alexa differ from many other IoT devices in that entering sleep mode must be balanced with the ability to react to a wake-up command.

There is also an increasing desire for products to operate in harsher conditions, whether it be in the rain, in the desert, on a factory floor, or on a wristwatch. A device that incorporates a microphone needs to be able to withstand those environments, despite reliance on pressure waves in the air being able to reach the active element that drives the microphone.

Vesper and other microphone manufacturers are up against these demands and issues with each component they manufacture.

If you have experience designing low-power devices with a voice interface, tell us about how you've solved these challenges in the comments below!

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