Examination: Sound insulation with open window?
Noise-reducing headphones are now standard. In airplanes, on trains or on the street: in noisy places, more and more people wear noise-reducing earphones to enjoy music undisturbed. Researchers at Nanyang Technological University in Singapore have now investigated whether the technology is also suitable for protecting homes against street noise. The results are interesting.
From headphones to the window
The way noise cancelling technology works is simple. A microphone detects the noise coming from outside and transmits the information to a connected loudspeaker, which generates a signal with reversed polarity. The sound waves coming from the outside are thus opposed in exactly the opposite way, so that the wave crest and wave trough meet. This in turn has the effect of neutralising the sound to a certain extent. This technology works perfectly with headphones, not least because they only have to react to a very limited sound volume.
Nevertheless, researchers at Nanyang Technological University are now trying to use this technology to reduce noise in homes. A window measuring 1 x 1 meter with an open area of 0.45 x 0.93 meters was used to investigate the feasibility. A total of 24 loudspeakers with a diameter of 4.5 centimeters each were installed in front of the window. The loudspeakers were arranged in eight rows of three. A security grill installed in front of the window was used for mounting – such grills are largely unknown in this country, but are widely used in Southeast Asia.
Not marketable for a long time
It turned out that the installation reduced the noise pollution in the apartment by about ten decibels. Such a reduction in noise pollution can also be achieved by closing the window – so the magnitude can be heard and felt. At frequencies below 300 Hertz, however, the noise reduction did not work, which in the study was attributed to the size of the loudspeakers used.
Such a technology is certainly still a long way from being ready for the market. Nevertheless, the initial results are quite promising, as it is a comparatively simple method of noticeably reducing noise pollution in homes and thus a massive health hazard. Further investigations remain to be seen. However, in a few years it may be perfectly normal to install not only insulating windows but also loudspeakers in front of these windows to reduce noise.