A MEMS startup firm, xMEMS, promises “a better way to hear audio” with its new all-silicon, solid-state microspeakers.

The speakers are designed for use in wireless stereo earphones, in-ear monitors, digital hearing aids, smart glasses and sleep buds. Two of the company’s MEMS devices are already in consumer products. Its Montara Plus full-bandwidth transducer is in Singularity Audio’s Oni in-ear monitor. A hearing aid from Digisine uses xMEMS’ Montara device, described in company literature as “the world’s first true MEMS full-range microspeaker.”

The FDA’s 2022 rule extending over-the-counter access to hearing aids for those with mild to moderate hearing loss promises to be a boon for the company if it leads to higher sales volumes overall.

“There’s about 20 more consumer products coming out throughout the rest of this year, and then the pipeline behind that, into 2024 and 2025, will continue to grow,” xMEMS’ Mike Housholder told EE Times. “So we’re at the very earliest point of market adoption.”

A third new xMEMS device, Cowell, described by the company as “the world’s smallest solid-state microspeaker,” is just starting mass production shipments.

A fourth product, Skyline DynamicVent, promises to allow hearing aid and earbud wearers to switch between open-fit architecture, which lets in ambient noise from the environment, and closed-fit, which blocks sound.

Blocking all sound can amplify the sound of one’s voice or footsteps, which some find annoying. It can also be dangerous for, say, a runner wearing earbuds who can’t hear noise from traffic and other elements in his surroundings.

“With DynamicVent, we’re trying to enable a more dynamic form of consumer audio product that can better adapt to the user experience,” Housholder said.

Size matters

xMEMS’ “world’s only” all-silicon, solid-state devices are meant to replace the magnet and coil speaker technology that Thomas Edison, Alexander Graham Bell and Werner Von Siemens tinkered with longer than 100 years ago.

The modern devices were enabled by an advance in materials science.

“The trigger for making a monolithic MEMS speaker a reality was the creation of thin film piezo materials back in 2015,” Housholder said. “They presented a material that could be a layer in the semiconductor fabrication process to serve as the actuator for the speaker.”

Those materials and xMEMS’ technology led to speakers that are about 10% of the weight and 40% of the size of a similar coil speaker, according to company literature. The weight and size reduction enables their use in small components like earbuds and hearing aids.

Not only are they smaller and lighter, the company’s tech used in Bluetooth-enabled hearing aids may lead to an enhanced user experience, Housholder added.

“We’re even smaller than the incumbent speaker technology [in a hearing aid], and we are wide, full bandwidth,” he said. “So now you have a speaker that… produces a wider spectrum of sound to play media and voice.”

The silicon membranes used in xMEMS speakers have been shown to be 95× stiffer than conventional speaker membrane materials, which results in improved clarity and eliminates the “muddy midrange and treble response” of traditional speaker membrane materials, according to company literature.

“The silicon architecture also delivers 150 times faster impulse response than traditional designs, offering the most pulse-true and accurate sound reproduction, which is not possible with the slow attack and decay of coil architecture,” according to remarks prepared by xMEMS.

While xMEMS is a startup, its people aren’t new to MEMS development and production: A group of former InvenSense employees opened the Santa Clara, California-based company in 2018.

InvenSense designed MEMS gyroscopes and accelerometers and, like xMEMS, contracted with the TSMC fab to produce its products.

TDK acquired InvenSense for $1.3 billion in 2017.

While xMEMS is concentrating on personal audio now, its advanced R&D is tech for full-bandwidth audio in free air. Housholder compares his company’s efforts to disrupt the speaker market to that of microphones, which started their transition to the modern technology in the mid-2000s.

“Now MEMS microphones are the dominant microphone type in the industry versus the old mechanical variant,” he said.

MEMS’ use growing

xMEMS’ devices join a growing list of MEMS technology used in consumer and other products since the invention of the first microelectromechanical system in 1965 at Westinghouse Research Labs. They include accelerometers for airbag sensors, inkjet printer heads, computer disk drive heads, blood pressure and other biosensors, and optical switches.

“This area of MEMS—audio—is a truly exciting and growing area with several players chasing after the market,” Roger Grace, president of Roger Grace Associates, an independent technology marketing consultancy that specializes in sensors and MEMS, told EE Times. “It all started over two decades ago with MEMS microphones. From a MEMS speaker perspective, Usound, in Austria, is a major player in the MEMS speaker area and should be considered a significant competitor of xMEMS. Other major players currently chasing MEMS acoustic opportunities include Analog Devices, ST, Bosch and TDK/InvenSense.”

By: DocMemory
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