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Friday, January 05, 2018

On-chip micro-speakers drive new embedded design options

By Nick Flaherty

STMicroelectronics has delivered the first micromachined on-chip loudspeakers resulting from its collaboration with Usound. 

The MEMS devices are expected to enable the thinnest in the world and less than half the weight of conventional speakers, enable wearable tech such as earphones, over-the-ear headphones, or Augmented-Reality/Virtual-Reality (AR/VR) headgear to become even more compact and comfortable. The extremely low power consumption saves extra weight and size by allowing smaller batteries, and unlike conventional speakers they generate negligible heat.

MEMS technology using standard CMOS chip-making technology is already being used for  navigation, tracking, and other features. With MEMS now coming to speakers, designers can further miniaturise the audio subsystem, reduce power consumption, and create innovative features like 3D sound. 

The advanced MEMS micro-speakers feature a piezo-electric actuator that deflects in response to analogue audio signals as an alternative to the conventional electro-mechanical speaker. The new devices also eliminate the usual trade-offs between magnet size, air volume, and sound quality that complicate both the design and integration of traditional, conventional electro-mechanical miniature speakers that contain a magnet and balanced-armature mechanism.

USound's patented concept for these speakers leverages piezo-electric material properties to drive the speaker membrane, which eliminates the complex signal processing required in other types of MEMS micro speakers. The piezo actuator allows an extremely small speaker footprint and low profile, with outstanding power efficiency and fast response for high acoustic performance.
MEMS-industry analyst Yole Développement values the overall micro-speakers market at $8.7 billion currently, and expects MEMS manufacturers to capture share with silicon-based devices.

"This successful project combines USound's design flair and ST's extensive investment in MEMS expertise and processes, including our advanced thin-film piezo technology PeTra (Piezo-electric Transducer)," said Anton Hofmeister, Vice President and GM of MEMS Microactuators Division, STMicroelectronics. "Together, we are winning the race to commercialise MEMS micro-speakers by delivering a more highly miniaturised, efficient, and better-performing solution leveraging the advantages of piezo-actuation."

"ST has provided the production expertise and manufacturing muscle to realise our original concept as a pace-setting, advanced product ready for consumer-market opportunities," said Ferruccio Bottoni, CEO of USound. "These tiny speakers are now poised to change the design of audio and hearable products, and open up new opportunities to develop creative audio functionalities."

The new piezo-actuated silicon speakers support innovation in a wide variety of hearable electronics, including home digital assistants, media players, and IoT (Internet-of-Things) devices.

USound will demonstrate prototype AR/VR glasses containing multiple MEMS speakers per side next week at CES 2018 with advanced features such as beam forming for private audio.

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