Digital MEMs Microphone Extends Smart Speaker Battery Life by Ten Times

July 30, 2020 by Jake Hertz

The power-saving architecture behind the MEMs microphone side-steps the pitfalls of always-on listening battery consumption.

Smart speakers are one of the most popular pieces of consumer electronics to reach the market in the past ten years. These speakers introduced a new concept in voice activation: the always-on voice command.

As opposed to older voice-activated speakers that listen to commands when a push-button is pressed, new smart speakers are constantly listening for their wake-up command (think “Alexa” or “Hey Google”). 


Depiction of a smart speaker listening for a wake command.

Depiction of a smart speaker listening for a wake command. Image used courtesy of Consumer Reports


The problem here is that to constantly be listening for a command means that the system is constantly consuming power. This is one of the main reasons why smart speakers are conventionally plugged into wall outlets for power. This is also one of the major privacy concerns with smart speakers: they’re literally always listening to us! 

Now with an increased demand for portability, designers have to come up with a way to work around these issues and make these devices more efficient on battery operation.  


Vesper's New Digital Piezoelectric MEMs Microphone

Well aware of these issues and the growing demand for battery-powered smart speakers, MEMs microphone specialists Vesper has been working on a solution. 



VM3011. Image used courtesy of Vesper


Just this week, Vesper announced the release of their VM3011, which they are calling the world’s first adaptive ZeroPower listening digital piezoelectric MEMs microphone. Vesper has a long line of piezoelectric MEMs monolithic microphones aimed at reducing power consumption and increasing reliability in noisy environments.

Now with this new smart speaker-facing product, they have introduced the possibility for drastic improvements in power consumption.


Vesper’s Adaptive ZeroPower Listening Technology

This new device integrates both the ASIC and the transducer on the same package, providing its unique functionality.

VM3011 makes itself unique and useful by utilizing Vesper’s adaptive ZeroPower listening technology. With this technology, the microphone actually learns the acoustic characteristics of its given environment. In this way, the system is able to ignore background noise and only wake in response to keywords or other desired acoustic triggers that are above the standard threshold.


Potential application circuit

Potential application circuit. Image used courtesy of Vesper


In ZPL mode, when the threshold is crossed, the VM3011 sends a “threshold exceeded” flag to the DSP to activate it and process the audio. This becomes extremely valuable since the DSP will only be triggered when the threshold is crossed. Instead of conventional operation, where all sound is processed by the DSP in order to see if the wake-command was heard, now the DSP triggers significantly less, and only when necessary. 


How Vesper Extends Battery Life

When in ZPL mode, the device only consumes 10 μA.

According to Dr. Paul Beckmann et. al, “Considering the batteries in portable products typically dissipate about 50 μA of power even when fully powered off, the VM3011 has virtually no effect on the battery life of a portable product. Most importantly, these ZPL microphones all the rest of the system hibernate in very-low-power modes, while the ZPL microphone monitors the environment and wakes up the processor when certain sounds occur.” 

Vesper claims that the VM3011 allows the full system to hibernate up to 90% of the time and can increase system battery life by 10x. 


Greater Longevity for Smart Speakers

This solution looks promising to increase battery life in voice-activated products such as smart speakers. A ten times improvement in battery life will undoubtedly make smart speakers, and other related products, more viable as battery-operated devices.

On top of this, the VM3011 will likely have the unintended benefit of mitigating privacy issues, as a system will listen to and process less of the environment. 

With the ease of integration and power savings offered by the VM3011, it seems likely that this technology, or one similar, will find its way into smart homes very soon.