The Hyogo National Highway Office of the Japanese Ministry of Land, Infrastructure and Transportation (MLIT) has constructed Japan's first noise barriers with loudspeakers. The operating principle of the device used in these new barriers is to reduce traffic noise by generating anti-phase sound.

In a split second, the noise-reducing device picks up traffic noise with microphones and transmits the noise signal to its control circuit in order to generate anti-phase sound, which it emits through loudspeakers. This anti-phase sound counteracts the noise, and the two noises eliminate each other. The Ministry reports that the device's noise reduction effect was about 4 decibels in its experimental stages.

The devices are to be fitted to the top of existing 4.5 meter high noise barriers. MLIT's National Institute for Land and Infrastructure Management co-developed this new device with Mitsubishi Heavy Industries, Ltd.

The new noise barriers were put up in front of Seidou Elementary School in Ashiya City, located along National Route 43 in Hyogo Prefecture. Barriers were built along 150 meters of the Kobe-to-Osaka side of the road, and along 110 meters of the Osaka-to-Kobe side of the road, construction having been finished on March 26, 2004. The ambient noise level in this area has sometimes exceeded the allowable limit of 65 decibels at night, and the new barriers are expected to reduce this noise. Officials plan to monitor the noise reduction effect of the barriers and their durability.




Posted: 2004/05/31 08:47:51 AM
Japanese version

TAG Government , Manufacturing industry , Other , Technology , Transportation , University/Research institute