The smallest MEMS loudspeaker in the world

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It’s the smallest loudspeaker in the world, but they say it makes some big noise. MEMS makes it possible. These micro electro-mechanical systems have shrunken microphones, cameras and an entire range of sensors for smartphones, wearables and the like to a sub-millimeter scale.

It has taken nearly 150 years for semiconductor technology to replace Werner von Siemens’ proven loudspeaker principle from 1877 in various sectors. Coil-magnet combinations are still being used to make diaphragms vibrate in smartphones, wearables and headphones. Although the design has gone through a number of miniaturization processes, it still looks ancient compared to its new competitors made of silicon. Among other things, that is because its efficiency is simply catastrophic. In some Hi-Fi speakers, 99 percent of the electrical energy dissipates in the form of heat in the bass range.

The MEMS loudspeaker (micro electro-mechanical systems) developed by USound, a start-up in Graz, has some other numbers to offer. It measures just 5 x 7 x 2 mm and has a frequency range of 2 to 15 kHz. It takes up half the space of its predecessors and needs only 20 percent of the energy that they do.

You have to wonder why none of the “big names” and, with the exception of Audiopixel in Australia, none of the “little names” came up with the idea of developing loudspeakers based on MEMS. After all, MEMS microphones have been paying attention to users’ voices for quite some time now. For example, there are four of them in the iPhone 6s. Quite a few of them come from STMicroelectronics. That is interesting because USound’s two founders, Andrea Rusconi Clerici and Ferruccio Bottoni, acquired their MEMS know-how there. Then they got together with Jörg Schönbacher, the third founder in the group, at Sensordynamics in Graz. Among other things, the company partnered with EnOcean to develop the world’s first SoC (system-on-a-chip) for energy harvesting based on the piezoelectric effect.

That is exactly what makes sure that a MEMS loudspeaker speak loudly. To that end, thin piezoelectric layers are applied to silicon. An electric signal makes it and the diaphragm connected to it move. Ultimately, the mechanical principle corresponds to that of a normal loudspeaker. However, the magnet and coil are replaced by a piezo element. That is nothing new. However, until now, piezo loudspeakers were unable to provide high sound quality or high sound pressure levels at low frequencies. But USound’s MEMS version appears to offer significant advantages when it comes to distortion and THD.

Partners and other participants

Developing and manufacturing this kind of ultra-small component calls for highly specialized know-how in several areas. And start-ups can’t build up that kind of expertise in a short period of time. That is why a number of Fraunhofer Institutes (IDMT, ISIT, IIS, IZM) and PCB specialist AT&S are on board.

Besides first-rate technology partners, new high-tech companies also need “participants” with suitable backgrounds. eQventure is the lead investor, so an old acquaintance of the founders is involved in the project. Herbert Gartner founded SensorDynamics and sold it to Maxim Integrated in 2011. Business angel Hermann Hauser, founder of British chip manufacturer ARM, came with him. The latter was sold to the Japanese technology company Softbank for 31 billion dollars. In other words, plenty of heavyweights for such lightweight “components.”

MEMS loudspeaker in mass production

Still, developing a prototype is only part of the journey. Producing large quantities is at least just as challenging. That is why the company just secured a 12 million euro growth investment. The first production line should be finished by the end of June, and deliveries will start going out to customers during the second half of the year. However, before the “piezos” can start making noise in smartphones, first they have to prove themselves in earphones. Smartphones are planned for 2018. The market could not be more lucrative for a “first mover”. According to the Yole Développement market research institute, MEMS sales are expected to increase to 20 billion dollars by 2021.


MEMS loudspeaker (Image: Usound).

MEMS loudspeaker with extremely small dimensions along with low power consumption and good sound quality. (Image: Usound).