Sonexos Raises €5.4 Million to Scale Plasma-Based Noise Control

Swiss DeepTech startup Sonexos has raised approximately €5.4 million (CHF 5 million / USD 6.1 million) in equity financing to move its solid-state noise control from working prototypes into industrial production.

Valquest Partners led the round, with participation from Robert Bosch Venture Capital GmbH (Bosch Ventures) plus industry angels and private investors. Fadi Noureddine, founder and Managing Partner of Valquest Partners, has joined the Sonexos Board of Directors.

"Engineers have always had to trade space and weight for silence. Plasmacoustics removes that compromise. This financing carries it from working prototypes into our customers' products, at scale," said Mark Donaldson, founder and CEO of Sonexos.

Donaldson founded the Lausanne-based company in 2022. He previously built SoundChip, which developed noise-cancelling smart audio codecs for headphones and earbuds from leading consumer electronics brands and was acquired by DSP Group, now part of Synaptics.

Why low-frequency noise is the hard problem

Sonexos targets the persistent low-frequency hum from fans, compressors and motors — noise that carries through walls and windows and is the hardest to eliminate. Conventional acoustic treatments become bulkier at lower frequencies and can restrict airflow. Loudspeaker-based active noise cancellation works in a headphone's confined space but struggles with complex, three-dimensional sound fields in real-world settings.

The company's answer is its patented Plasmacoustic Metalayer: a software-controlled plasma layer that absorbs sound at a surface. The system is thin, lightweight and has no moving parts, enabling electronically programmable control for domestic appliances, HVAC, industrial, infrastructure, automotive and specialised acoustic applications.

The numbers are concrete. Prototype systems have achieved up to 20 dB of low-frequency noise reduction in ventilation systems and 16 dB in domestic appliances under application-specific test conditions.

What does this change for OEMs?

Two product lines carry the technology. Plasmapanel packages the plasma metalayer into a sealed, inert-gas-filled module driven by proprietary low-power, high-voltage electronics. Plasmadrive is the electronics and software side of the platform.

Depending on installation, Plasmapanel-enabled systems absorb sound from 30 Hz to 1,500 Hz and, versus passive silencers with similar low-frequency performance, need less than a fifth of the space and weight. For OEMs, that frees room for more compact products or for features that bulky acoustic treatment would otherwise displace.

Sonexos is building an industrial ecosystem rather than manufacturing everything in-house. STMicroelectronics is supporting development of low-power, low-cost electronics. A strategic collaboration with Vandewiele Group, through its subsidiary Roj, provides a route to series manufacturing for European OEM programmes, including electronics production, box-build and cabling.

The go-to-market model has two tracks: turnkey panels with integration support, and an enterprise model where larger OEMs embed Sonexos components such as Plasmadrive, plus software, into their own products and production lines.

The data-centre angle

Sonexos also plans expansion into AI data-centre cooling, where reduced fan noise could ease community concerns and help sustain cooling capacity under night-time noise limits. It is developing the Plasmapanel Radial Active Silencer to mount around a fan discharge and attenuate low-frequency sound without obstructing airflow.

In July 2026, Sonexos announced a collaboration with Euronext Milan-listed SIT to integrate the technology with fan platforms for data centres, battery energy storage and industrial cooling. SIT is the first member of the Sonexos Certified Fan Partner Programme, and the partners plan to show a first working demonstrator at CES 2027.

"Sonexos is addressing a fundamental engineering constraint with a technology that opens a much larger design space for low-frequency noise control. The combination of differentiated science, a strong intellectual-property position and progress with leading OEMs gives the company a credible path toward industrial production," said Noureddine.

The new capital will fund industrialisation of the core platform, customer integration, reliability testing, qualification and regulatory compliance, expansion of engineering and applications teams in Switzerland and internationally, and broader international IP protection. Sonexos holds an exclusive licence from EPFL to foundational plasmacoustic patents in its field of use, has filed four additional patent families of its own, and has two UK patents granted with applications pending in other major markets.

If the CES 2027 demonstrator with SIT performs, plasma could move from lab curiosity to a specified component in data-centre cooling contracts — a market where noise limits are increasingly a capacity constraint.