Vesper Piezoelectric MEMS Microphone with 68 dB SNR

-June 11, 2015

Usually, when an architecture has reached its limits of performance, some radical new game-changing idea needs to be implemented. A company known as Vesper has been promising just that since I first met CEO Matt Crowley at the MEMS Executive Congress in 2014. Now this projected $5.4B projected market in 2017 has a new player that is shaking up the very high-performance segment of high Signal-to-Noise (SNR) with numbers in the range of 64 dB. Vesper has radically shifted the technology architecture which uses a unique piezoelectric design that will eclipse capacitive architectures.

This product is featured in EDN's Hot 100 products of 2015. See all 100 here.

Vesper’s recent launch of the VM101, a piezoelectric MEMS (microelectromechanical systems) microphone has achieved 68 dB typical signal-to-noise ratio (SNR) -- the highest acoustic-performance benchmark of any commercially available MEMS microphone in the industry.

This is the first ultra-high SNR MEMS microphone and its unique architecture solves major performance issues facing consumer products manufacturers. This new design, first developed by founders at the University of Michigan in 2009, enhances the quality and clarity of audio capture to improve the voice user interface in smartphones, wearables, smart home appliances and Internet of Things (IoT) devices. I was told that this type of architecture was conceived back in 2006 when a cochlear implant model was built with it.

The MEMS industry executive team joined with these founders and launched Vesper in 2014.

Matt Crowley told me at the MEMS Executive Congress last year his prediction:

Voice is expected to supplant touch as the dominant user interface in consumer products. This makes higher-performance MEMS microphones increasingly critical because they are right at the beginning of the audio signal chain. 

So not only is this the highest SNR device in the market, but it is also the only MEMS microphone that is waterproof, shockproof and dust- and particle-resistant – greatly helping to solve reliability issues with existing products.

Here are some test results:

A metal mesh used in a capacitive  microphone to block dust and water can easily clog up especially with surfactants (soaps) or salt water, sweat or winding up in the laundry.

Water

 In port-side up orientation, the VM101 passed the most difficult water test for microphones. Some companies only test this port-side down.

 

 

The VM101 was pressurized to a 5 meter depth for 30 minutes. Its unique design eliminates water failures.

There is no measurable shift in performance pre- and post-water exposure for the VM101.  


Dust

An industrial test adaption was done which had an average particle size of 6 microns. Dust was sprayed for 10 seconds.

Capacitive microphones are sensitive to dust accumulation:

 

A magnified view shows how dust sits on the capacitive microphone sensor.

 

 

This graph shows capacitive microphone performance before and after dust contamination.

The VM101 has proved to be impervious to dust by its very architecture:

 

There is dust on the VM101 structure, but the architecture is not affected nor is the sensitivity.

 


This graph shows VM101 microphone performance before and after dust contamination--virtually no effect on sensitivity.

       

Crowley added:

You can actually drop VM101 into Boston Harbor or bury it in sand at the beach, and it will still work properly. With microphone failure the second most common reason for smartphone returns after cracked screens, reliability is vital. Having such a robust microphone potentially alleviates major headaches (and returns) for manufacturers.

The innovative new architecture

If we look at a capacitive microphone element design, we find a diaphragm which flexes as the sound waves strike it. There is also a backplate in this design that holds the diaphragm. This design introduces a barrier to the incoming sound and in-turn limits dynamic range due to this architecture.

 

In the VM101 piezoelectric MEMS design, incoming sound impinges on the moving plates which have an opening for the sound to not be compressed as in the capacitive design.

 

SNR performance

This microphone design achieves 68 dB SNR, nearly doubling the performance over the current high-end 65 dB SNR capacitive MEMS microphones. Customers wanting always-on far field voice user interface with noise cancellation will like how the VM101 far-field audio doubles the distance of sound capture.

Also in simple smart phones this microphone can enhance ambient noise cancellation that dramatically improves the clarity of phone conversations and enhance the user experience with other voice-enabled applications like smart home devices, and smart TV remote controllers that allow consumers to navigate menus, surf the Internet and record programs using voice instead of touch. I really see this technology replacing infrared and RF controllers.

Customers also want to match audio quality of high-end video cameras  and by using the “audio zoom” recording feature for sound/video recording with ambient noise cancellation, this becomes a reality. I wish I had this for my niece and nephew’s wedding last year as jet aircraft from the local airport zoomed overhead and drowned out the minister’s words and their responses. I had to by a special audio program to correct it.

Microphone Arrays

MEMS microphones are typically used in microphone arrays of up to four microphones, which makes microphone stability critical. Higher SNR microphones enable larger arrays and give audio processors more signal with which to work. Arrays also give directionality and focus; they can be used with signal processing for effect at the push of a button. Be cautious because endlessly increasing the number of microphones in array will eventually give diminishing returns and actually hurt SNR.

 

Capacitive MEMS microphones are prone to drift once they leave the factory, Vesper piezoelectric MEMS microphones are exceptionally stable, making them ideally suited for microphone array applications such as:

  • far-field audio – improves sound capture, even at longer distances
  • ambient noise cancellation – enhances clarity and intelligibility for recording or speaking on the phone
  • “audio zoom” – focuses on a single sound source when recording, enabling more accurate sound-selection

Other unique Technical Specifications


  • standard 3.35 x 2.50 mm package size – drop-in replacement for capacitive MEMS microphones. A flip-chip and a thinner package can also be done in the future with this technology.



  • Rapid start-up <10 msec
  • 150 uA typical power consumption


Availability

VM101 is currently sampling from Vesper with production volumes slated for Q4 2015. For sales inquiries, contact Vesper via phone: +617.315.9144 or email: info@vespermems.com or visit Vesper on the web: www.vespermems.com.


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