Device makers are going all-in with voice-forward technology, bringing magical hands-free voice experiences to a wide range of at-home and on-the-go products. However, standard MEMS microphones typically don’t withstand the wear and tear of harsh environments. As device makers invest in integrating Alexa into on-the-go products, they need durable microphones that enable them to build hands-free voice experiences that are flexible enough to withstand constant environmental extremes.

This post covers best practices for selecting the right microphones for your product’s mic array and explains the core differences between standard capacitive microphones and piezoelectric MEMS microphones, a new breed of technology pioneered by Vesper Technologies, an Alexa Fund portfolio company.

Growth of Voice-Forward Devices

The Alexa Voice Service (AVS) enables developers to add Alexa, cloud-based intelligence, and hands-free voice control to a variety of products, from smartphones and smart speakers to automobiles and wearables. With the introduction of new voice-forward products, device makers need to consider how the environment in which their product will be used will impact the components adopted during device design.

Standard Microphone Shortcomings in Rugged Environments

Products that feature arrays with four or more microphones offer clearer audio pickup, and enable Alexa to understand user intent and respond with the appropriate answer. Larger microphone arrays are also more fragile as each component plays a crucial role in how the device works. Large microphone arrays used in harsh environments could result in a low-quality customer experience as the device experiences normal wear and tear. As device makers look for ways to build Alexa-enabled mobile products, they need to rethink hardware design to provide more reliable voice experiences to customers. One major hurdle is microphone selection.

When used in large arrays, standard capacitive MEMS microphones are easily damaged by common environmental contaminants such as water, dust, and particulate matter, for three core reasons:

• An array relies on the functioning of every microphone working in unison, and one bad microphone can throw off its performance.
• If dust enters a microphone array, it often interprets sensitivity shifts as directionality cues. The additional functions such as locating a sound source can become noticeably impaired.
• Large array beamforming often requires fitting microphones in vulnerable locations, which increases their chance of failure.

Piezoelectric MEMS Microphones

Piezoelectric MEMS microphones offer a new low-power solution without mechanical compromises that enable device makers to add larger mic arrays into devices used in inclement environments both inside and outside of the home. Vesper Technologies has invented the first commercially available piezoelectric MEMS microphone. Its main difference is that it does not need a back plate, enabling the flexible microphone plates to bend and experience stress without quality degradation. In contrast, standard capacitive MEMS feature a diaphragm and a back plate, creating a small gap between the two. As the diaphragm is distorted by sound pressure, the gap between the two areas increases allowing dust and other particles to enter the space and harm the microphones. The piezoelectric MEMS design replaces the diaphragm and back plate with flexible alternatives that result in a waterproof, dustproof, particle-resistant, and shockproof microphone that requires no workarounds to be used in high-reliability arrays.

Vesper microphones make it possible for device makers to use large arrays without worrying about mic failure due to debris or needing additional mesh coverings or membranes.

Low-Power MEMS Open the Doors for New Use Cases

In addition to offering a durable alternative to capacitive microphones, Vesper’s piezoelectric MEMS are low-power and enable device makers to implement a wake-on-sound solution. Capacitive MEMS often consume more power than piezoelectric microphones, making it difficult to develop an on-the-go device that demonstrates a longer battery life with a voice-forward design.

Vesper Technologies

In December 2016, the Alexa Fund added Vesper to its portfolio by contributing to its Series A round of funding to accelerate the adoption of voice-first interfaces across multiple device types and use cases.  Vesper’s MEMS microphones use a patented piezoelectric design to prevent dust, water, solder flux vapors, and more from impacting performance, presenting a unique opportunity for OEMs and ODMs to build products for a variety of use cases.

The Alexa Fund

The Alexa Fund provides up to $100 million in venture capital funding to fuel voice technology innovation and builds on Amazon’s track record of enabling individuals to grow ideas into successful products and businesses. Amazon helps accelerate ideas by offering unique benefits to development teams, such as early access to Alexa capabilities and enhanced marketing support across channels. Learn more about the Alexa Fund and its portfolio of companies on the Amazon Developer Portal.