This Swiss Startup Just Raised $6.1M to Silence the Hum You Can't Escape

Jan de Vries · 2026-10-26

Ever notice that low, persistent hum from your fridge, fan, or the data center down the street? It's the kind of noise that burrows into your brain and never lets go. Well, a Swiss startup called Sonexos just raised about $6.1 million to tackle exactly that—and they're doing it with plasma. ### The Problem with Low-Frequency Noise Low-frequency noise is a stubborn beast. It slips through walls, windows, and just about anything else. Traditional soundproofing materials get bulky and heavy when you try to block it, and they can even restrict airflow. Active noise cancellation (ANC) works great in headphones, but in a real room or a factory floor? Not so much. The sound field is too complex. Sonexos claims its patented Plasmacoustic Metalayer uses a thin, software-controlled plasma layer to absorb sound right at the surface. No moving parts, lightweight, and it can be programmed electronically. In tests, their prototypes have cut low-frequency noise by up to 20 dB in ventilation systems and 16 dB in home appliances. That's a big deal. ### From Prototypes to Production Sonexos was founded in 2022 by Mark Donaldson, a serial entrepreneur who previously built SoundChip (acquired by DSP Group). The company's Plasmapanel technology packs the plasma layer into a sealed, inert-gas-filled module. It absorbs sound from 30 Hz to 1,500 Hz and takes up less than a fifth of the space and weight of passive silencers. For manufacturers, that means more room for features or smaller products. The recent funding round was led by Valquest Partners, with participation from Bosch Ventures and private investors. Fadi Noureddine from Valquest has joined the board. "Engineers have always had to trade space and weight for silence," Donaldson said. "Plasmacoustics removes that compromise." ### Building an Ecosystem, Not Just a Product Sonexos isn't trying to make everything in-house. They're partnering with STMicroelectronics for low-power electronics and with Vandewiele Group (via its subsidiary Roj) for series manufacturing. They plan to offer turnkey panels and an enterprise model where OEMs integrate Sonexos components into their own products. Next up: AI data-center cooling. Reduced fan noise could ease community complaints and help data centers operate more quietly. With this fresh capital, Sonexos is moving from lab to factory floor—and that hum you've been ignoring might finally meet its match. > "Engineers have always had to trade space and weight for silence. Plasmacoustics removes that compromise." — Mark Donaldson, CEO of Sonexos So next time you hear that annoying drone, remember: someone's working on it. And they're using plasma to do it.