Among the cacophony of car horns and screeching tires in Zurich, a material from the Swiss Federal Laboratories for Materials Science and Technology (EMPA) is making noise reduction a whole lot quieter. This mineral foam is four times thinner than conventional sound absorbers but just as effective. For architects and builders it’s a sleek and efficient way to dampen city noise without sacrificing space.
Made from gypsum or cement, this foam doesn’t block sound – it redirects it. Led by researcher Bart Van Damme, EMPA’s team designed the foam with layers of different pore sizes and perforations, a labyrinth that forces sound waves to weave through and lose energy. A 2.1-inch thick panel can reduce traffic noise by up to 4 decibels, perfect for cars passing driveways or courtyards. It’s as effective as thicker materials but fits in cramped urban spaces.
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The foam’s versatility is what sets it apart. Unlike rigid sound barriers, it can be tailored to specific frequencies. For traffic noise between 500 and 1,000 Hz, the pore sizes and layer thickness are adjusted accordingly. For low rumbles in large halls or mid-range chatter in classrooms, the foam’s structure is fine-tuned using a numerical model that simulates air flow through its pores to get precise acoustic performance for each environment.
Practicality is a big plus. Fireproof, weatherproof and recyclable, it’s durable and eco-friendly. Easy to cut and install, it’s suitable for noisy stairwells and busy offices, outdoor façades. In a Zurich test, EMPA placed 72 panels over 130 square feet of a driveway between a busy street and a courtyard and it softened the passing car noise. This gives architects design flexibility without bulky insulation and residents quieter living spaces.
There are challenges – perforating the foam is a manual process so production is slow. It outperforms rock wool at low frequencies but lags on high pitched sounds. EMPA is working with Swiss material maker De Cavis to streamline manufacturing for scalability. If it works, this foam could soon line city streets, balconies and interiors and reduce the volume of urban life.
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