Tiny MEMS microphines provide excellent SNR & low power use

According to IHS, the MEMS microphone market will exceed $1.4Bn by 2018, almost doubling in size from 2012, with high performance microphones (over 64dB SNR) being the quickest growing and largest segment of the market. This growth is being fueled by an increased focus on voice-input quality by smartphone manufacturers who are integrating multiple MEMS microphones into each smartphone to achieve improved noise suppression and speech recognition accuracy for their end users.

In recent years, MEMS microphones have also become increasingly important for use in wearable devices which rely on voice as a key UI such as headsets, smart glasses and smart watches. These space-constrained, battery-operated devices bring a set of acoustic challenges to device manufacturers who need microphones that are smaller and use less power, but still provide high acoustic performance, to address far-field use cases where the user’s mouth is further from the microphone.

Akustica’s microphones demonstrate the advantage of combining in-house MEMS, ASIC, and package design with in-house fabrication facilities. The microphones are the first to make use of ASIC design elements that optimise performance depending on the target market. The two devices are also the first to be built using a recently introduced MEMS architecture and fabrication process, which includes additional material layers and optimised thicknesses of current layers. The AKU151 is the world’s first microphone to use an advanced, metal-lid, direct-port package.

The final performance of a MEMS microphone depends not only on how each component of the design performs independently, but also on how all pieces interact and perform together as a microphone system. In particular, high performance MEMS microphone design requires outstanding modeling capabilities, broad system understanding, and tight control of all aspects of design and fabrication.

The AKU151, in its tiny 5.4mm³ package, presents consumer device manufacturers with a durable, RF-immune microphone in the top-port configuration. Unlike other microphones where a smaller package typically results in lower performance, the AKU151 delivers a high SNR of 65dB, almost twice the acoustic performance density (SNR/mm³) of any other top-port MEMS microphone. The AKU151 is also optimised for low power applications, consuming only 60µA during standard, full-performance operation, making it suitable for use in applications which require small, high performance microphones but have limited battery life.

The AKU350 is a robust, bottom-port, metal-lid, 9.1mm³ microphone with a single-ended output that provides an outstanding 67dB SNR and a tight +/-1dB sensitivity matching. With its high SNR and accompanying microphone-to-microphone uniformity, the AKU350 is optimised to meet the needs of smartphone manufacturers who use multiple microphones with noise cancellation algorithms. These algorithms rely on well-matched, high-performance microphones to deliver superior noise suppression and speech recognition accuracy to the end user.

Higher accuracy microphones can significantly improve the quality of sound recordings made with mobile devices.  This is particularly evident when one is making a recording of a quiet or distant sound whose signal level approaches the inherent noise level of the microphone.  As Akustica recently demonstrated at the Consumer Electronics Show in Las Vegas, making a recording using a microphone such as the AKU350 - with a higher SNR than a typical smartphone MEMS microphone - can eliminate the hiss that can often be heard in recording playback, resulting in a crisper, more realistic sound.

“Akustica’s customers continue to benefit from the unique combination of experienced designers and industry-leading facilities that we have at our disposal as part of the Bosch Group,” said Horst Muenzel, CEO and General Manager, Akustica. “Nobody else in the world has the capabilities that we have. This is what allows us to uniquely respond to our customer’s needs and to deliver innovative microphones with higher performance, more uniformity, greater robustness, and smaller footprints.”

Samples of both products are currently available.