Sonexos Raises CHF 5 Million to Bring Plasma-Based Noise Control to Series Production
Sonexos, pioneering plasma-based noise control, transforming how the world eliminates unwanted low-frequency sound in real environments, led by Mark Donaldson and the team, has announced CHF 5 million (approximately EUR 5.4 million / USD 6.1 million) in new equity financing. The Pre-Series A round was led by Valquest Partners, with participation from Robert Bosch Venture Capital GmbH (Bosch Ventures) and industry angels and private investors. Fadi Noureddine, Founder and Managing Partner of Valquest Partners, joins the Sonexos Board of Directors.
Sonexos is developing a new approach to low-frequency noise reduction, targeting persistent hum from fans, compressors and motors. Its patented Plasmacoustic Metalayer™ uses a thin, lightweight, software-controlled layer of plasma to absorb sound without moving parts, addressing limitations of conventional acoustic materials and speaker-based active noise control.
Prototype systems have demonstrated noise reductions of up to 20 dB in ventilation systems and 16 dB in domestic appliances under application-specific test conditions. The latest financing will support the transition from prototypes to industrial products, with Sonexos running paid integration programmes with global appliance and HVAC manufacturers. Its most advanced programmes target series production in early 2028, subject to integration, regulatory and product-development milestones.
“Engineers have always had to trade space and weight for silence. Plasmacoustics removes that compromise,” said Mark Donaldson, Founder and CEO of Sonexos. “This financing carries it from working prototypes into our customers’ products, at scale.”
“Sonexos is addressing a fundamental engineering constraint with a technology that opens a much larger design space for low-frequency noise control,” said Fadi Noureddine, Founder and Managing Partner of Valquest Partners. “The combination of differentiated science, a strong intellectual-property position and progress with leading OEMs gives the company a credible path toward industrial production.”
“Technology is most valuable when it moves out of the laboratory and solves problems people experience every day. Sonexos is a strong example of that principle: outstanding deep tech addressing a very tangible challenge, with applications ranging from the appliances in our homes to the infrastructure powering the digital economy,” said Dr. Ingo Ramesohl, Managing Director of Bosch Ventures. “What convinced us in particular is the credible pathway toward industrial scale.”
The Team and the Technology.
Sonexos was founded by CEO Mark Donaldson, a veteran of the active noise-control industry who previously built SoundChip, acquired by DSP Group, now part of Synaptics. Its core plasmacoustic technology was developed at EPFL by CTO Dr. Stanislav Sergeev and published in Nature Communications in 2023. COO Andrea Onetti brings more than three decades of experience at STMicroelectronics, where he most recently led its MEMS Sub-Group.
Across three hardware generations, the team has reduced system weight and volume by more than 80%, combining plasma architecture, low-power high-voltage electronics and adaptive control software. The goal is to extend active noise control beyond headphones to entire appliances and industrial installations.
Sonexos’ Plasmapanel® packages its plasma metalayer into a sealed, inert-gas-filled module powered by proprietary electronics. Depending on the installation, the technology absorbs sound across frequencies from 30 Hz to 1,500 Hz while requiring less than one-fifth the space and weight of passive silencers with comparable low-frequency performance. This could enable manufacturers to develop more compact products or free up space for additional features.
Building the Route to Production.
Sonexos is building an industrial partner network to scale production without manufacturing every component in-house. STMicroelectronics, through its ST for Startups programme, is supporting the development of low-power, low-cost electronics. A strategic collaboration with Vandewiele Group subsidiary Roj provides a pathway to series manufacturing for European OEMs, covering electronics production, box-build and cabling.
The company plans to offer turnkey panels with integration support, alongside an enterprise model that allows larger manufacturers to integrate the technology directly into their products and production lines using Sonexos components, including Plasmadrive™, and its software.
A Further Opportunity in Data-Centre Cooling.
The expansion of AI infrastructure is driving demand for cooling systems, including large fans and dry coolers that operate continuously. Low-frequency fan noise can be difficult to contain, creating challenges for operators balancing cooling capacity with noise limits and neighbouring communities. Quieter cooling systems could help data centres maintain performance without restricting airflow.
Sonexos is developing Plasmapanel Radial™ Active Silencer, designed to reduce low-frequency noise around fan outlets without obstructing airflow. In July 2026, the company announced a collaboration with Euronext Milan-listed SIT to integrate the technology into fan platforms for data centres, battery energy storage and industrial cooling. SIT is the first member of Sonexos’ Certified Fan Partner Program, with the companies planning to showcase their first working demonstrator at CES 2027.
Use of Funds.
The CHF 5 million funding will support industrialisation of Sonexos’ core platform, customer integration, reliability testing, product qualification and regulatory compliance. It will also fund the expansion of engineering and applications teams in Switzerland and internationally, alongside broader global intellectual property protection.
Sonexos holds an exclusive EPFL licence for foundational plasmacoustic patents within its field of use and has filed four additional patent families of its own. Two UK patents have been granted, with applications pending in other major markets.
