Advanced MEMS Microphones Drive Superior Hearing Aid Sensitivity and Reliability

In an era of an aging global population and escalating environmental noise, safeguarding hearing health has never been more critical. Modern users demand hearing aids that are smaller, consume less power, and deliver crystal‑clear sound—an ideal fit for MEMS microphone technology.

According to the World Health Organization, more than 5% of the world’s population—466 million people—suffer from disabling hearing loss, and an estimated 900 million individuals (one in ten) will be affected by 2050. Disabling hearing loss is defined as a hearing threshold exceeding 40 dB in adults or 30 dB in children in the better ear.

ResearchAndMarkets.com projects the global hearing‑aid market to reach $7.62 billion in 2023, growing at a compound annual rate of 6.4% between 2019 and 2023. The market encompasses hearing devices, cochlear implants, bone‑conduction systems, and diagnostic instruments.

A hearing aid’s core function—capturing ambient sounds for amplification—relies on its microphone. While electret condenser microphones have dominated the sector, MEMS (micro‑electromechanical systems) microphones are rapidly becoming the preferred choice.

“MEMS microphones offer the reliability, compactness, and electro‑acoustic performance required for hearing‑aid applications,” said Manuel Tagliavini, principal analyst for MEMS & sensors at IHS Markit, to Electronic Products.

Michael Knapp, VP of Communications & Investor Relations at Knowles Corp., highlighted the benefits: a robust design with minimal particle ingress, a leading sensitivity‑to‑size ratio, and programmable integrated circuits that deliver versatile, tunable performance.

Knapp added that since the first generation of hearing‑health MEMS microphones hit the market five years ago, they are expected to comprise more than half of all microphones used in hearing‑health devices by 2020.

Although the MEMS microphone market for hearing aids is still modest compared to mobile phones or earbuds, it is expanding rapidly. IHS Markit estimates growth from $8 million in 2017 to $48 million in 2022, with a 42% CAGR.

Tagliavini notes that MEMS technology now meets medical‑grade reliability. “After billions of units shipped in consumer electronics, MEMS microphones have achieved the durability required for medical use,” he said.

He added that advances in size, power consumption, and cost—driven by smartphone and earbud demands—translate directly to hearing‑aid benefits.

Recent progress in MEMS microphones extends beyond hardware. Sensor arrays now enable beamforming and far‑field sensing, while sophisticated algorithms classify sounds—human voice, background noise, etc.—and selectively amplify or attenuate them. These features, originally tailored for consumer electronics, are now indispensable for hearing‑aid technology.

Knowles, a pioneer in MEMS microphones since the late 1990s, offers third‑ and fourth‑generation hearing‑health platforms that push the limits of sensitivity and noise performance in ultra‑compact packages.

The MM20 platform delivers a 70.5‑dB signal‑to‑noise ratio (SNR) and a 121‑dB sound‑pressure level (SPL), making it the lowest‑noise, highest‑SNR‑to‑size ratio in the market. It combines an acoustic sensor, a low‑noise input buffer, and an output amplifier—ideal for wideband audio and RF‑immune applications.

The MM25 platform builds on this foundation with a programmable ASIC that offers high versatility and ultra‑low‑power operation (18 µA to 31 µA). It supports advanced beamforming and microphone pairing, allowing designers to tailor performance to specific hearing‑aid architectures.

Knowles anticipates that ongoing MEMS innovations will expand voltage and current ranges, unlock new applications, and further elevate electro‑acoustic performance for hearing‑aid manufacturers.

Knowles’s latest generation of hearing‑health MEMS microphones continue to shrink in size. (Image: Knowles Corp.)

Across the Atlantic, Sonion a/s specialises in micro‑acoustic and micromechanical technologies for hearing instruments and hearables. Erik Dashorst, key account manager at Sonion, explained that MEMS microphones are far less susceptible to environmental conditions such as humidity and temperature compared to electret microphones, and they can be reflowed directly onto PCBs, eliminating the need for wires and hand soldering.

Sonion’s O‑Series MEMS microphones, co‑developed with TDK‑InvenSense, come in two compact volumes—8 mm³ and 11 mm³. Key specifications include an average current of 31 µA, sensitivity ranging from –37 dB 1 V/Pa to –38 dB 1 V/Pa, and noise levels between 26 dB and 28.5 dB.

The new P‑Series offers improved SNR, higher sensitivity, and very low power consumption. Sensitivity spans –35.5 dB 1 V/Pa to –38 dB 1 V/Pa, noise between 24.5 dB and 25 dB, and a battery drain of 31 µA to 32 µA.

Dashorst highlighted that the P‑Series is engineered to be insensitive to external light sources—a common issue in semiconductor devices that can be mitigated through specific doping strategies. He also noted that further miniaturisation would increase noise, compromising usability.

Sonion’s upcoming Q‑Series delivers a flat response curve and minimal distortion (intermodulation distortion below 10 %). Unlike the P‑Series, the Q‑Series eliminates the low‑frequency peak that can cause undesired amplification around 10 Hz, without adding filter‑induced noise.

The Q‑Series retains similar dimensions to the P‑ and O‑Series (3.35 × 2.50 mm) while offering sensitivity between –35.5 dB 1 V/Pa and –37.0 dB 1 V/Pa.

In‑Lab Advances

Most commercially available hearing aids employ external microphones, which can cause discomfort, limit physical activity, and contribute to social stigma. There is an urgent need for implantable solutions that are minimally invasive yet highly sensitive.

Last year, the University of Zürich and the Cochlear Technology Centre Belgium announced research into a MEMS condenser microphone‑based acoustic receiver for totally implantable cochlear implants (TICI). The intracochlear acoustic receiver (ICAR) captures pressure fluctuations within the cochlea induced by the outer and middle ear chain, leveraging the ear’s natural amplification and directionality cues.

ams AG is working on new ways to treat tinnitus, developing a new therapy using environmental noise. (Image: ams AG)

ams AG, an Austrian company, is pioneering tinnitus treatment that harnesses environmental noise. Using active noise‑cancelling hardware, it transforms ambient sounds into a personalized tinnitus training signal. Verena Vescoli, senior VP of R&D at ams, reported that the therapy significantly reduces tinnitus severity, especially with frequent use, and yields lasting benefits.

MEMS microphones are steadily supplanting traditional electret microphones in hearing aids thanks to their reliability, robust construction, minimal particle ingress, compact size, and superior performance. Ongoing research continues to push the envelope, promising even greater sensitivity, lower noise, and expanded applications for the hearing‑health industry.