To combat noise pollution and its effects on human health, DeNoize, a start-up incubated at Mines Saint-Étienne, offers a solution: a window that ‘mutes sound’. This connected window would analyze outside noise and adapt to cancel it out.
Double glazing increases thermal insulation, but when it comes to noise, it’s another story. When we’re indoors at home or the office, the vast majority of the outside noise that reaches us comes through the windows. This is an especially big concern for people who live or work near airports or major roads. Since May 2018, DeNoize co-founders Olivier Schevin and Aman Jindal have made it their mission to reduce this noise pollution, which is detrimental to our health.
DeNoize, a start-up incubated at Mines Saint-Étienne, offers an innovative solution for improving sound insulation in windows. “Our challenge is now to miniaturize the system so that it can be integrated into window frames,” says co-founder Olivier Schevin. The concept could easily be integrated into standard windows available today.
The problem with double glazing
“Double glazing is actually less effective than single glazing when it comes to sound insulation for the same thickness of glass,” says Olivier Schevin. Although it may seem counterintuitive, double glazing offers less resistance to low frequencies— between 50 and 500 Hz. A frequency band that is the main source of noise from airports and roads. “Double glazing was designed to solve thermal insulation problems, without considering the acoustic aspect,” he explains.
Double glazing is first and foremost two masses, the panes, with air or gas between them. This structure poses a problem from an acoustic point of view: certain frequencies – low frequencies – causes the air trapped between the panes to resonate and the sound propagates. This effect may be counteracted by increasing the thickness of the windows, or the space between the two panes. This passive reduction results in a bulky look from an architectural viewpoint and is also very expensive.
Sound fights back
DeNoize’s innovation is to use sound to fight sound, making it an active noise reduction system. “We’re going to generate a counter-vibration suited to the vibration of the outside noise,” explains Olivier Schevin. “The system produces a vibration that counters that of the outside noise, creating a destructive interference.” The vibrations ‘cancel each other out,’ reducing the noise transmitted by up to 75% for low frequencies.
“This technology is somewhat similar to that used in noise-cancelling headphones,” adds Olivier Schevin. “The technical difference is the surface of the area we want to treat. For the headphones, it’s a really small area close to the ear.” The system developed by DeNoize users sensors to analyze outside noise in real time and adapt to it accordingly. The actuators produce a counter-vibration that interferes with the original noise. It must also include a control unit and an electronic board responsible for determining the most effective actions for sensors and actuators.
The system is integrated into the window frames and requires an electrical connection nearby to supply it with energy. This is already common today with rolling shutters for example. The innovation in step with advances in smart home technology.
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This communication between actuators, sensors and control unit makes it possible to customize noise reduction in real time which adapts to outside variations. “As of now, we have a working prototype,” says Olivier Schevin, “But the system doesn’t calculate in real time yet. So we still have a development phase ahead of us for the electronics part.”
Olivier Schevin is launching an industrial project with students to develop a real-time demonstrator. The electronic component is still to be developed, since the existing control unit was made using laboratory equipment that cannot be integrated into window frames. “In general, we’re still looking for ways to improve performance at the lowest possible cost.”