Kawasaki Develops Hybrid-type Soundproof Equipment

 Kawasaki succeeded in developing a new type of hybrid soundproof equipment in July, which is attached to noise barriers to improve the reduction of noise generated on roads and railways.

 The equipment adopts a hybrid structure that is composed of a resonance device and a noise absorption device to efficiently reduce noise over a wide frequency band. The resonance device is made up of three resonators, which are tuned into optimal resonance frequencies by adjusting the size of cavities and openings. This device reduces mainly low to mid frequency noise utilizing the sound interference effect from resonance. The noise absorption devices, which are filled with glass wool, are arranged around the openings of the resonators and are effective in reducing high frequency noise.

 When installed at the top of a three-meter high noise barrier, noise is decreased by an average of 4.5 decibels at a distance of 5-10 meters behind the barrier. This noise reduction is equivalent to raising the barrier another 2.5 meters.

 The equipment is lightweight and compact with a width of approximately 500 mm and can be easily attached to existing noise barriers without the need for reinforcement. Compared to conventional soundproofing measures such as increasing barrier height, this equipment has outstanding cost performance because reinforcement work is unnecessary. Furthermore, adverse influences on the surrounding area such as the blocking of sunlight and radio waves can be avoided. Because the equipment can efficiently reduce noise of a specific frequency, it can be used not only for roads and railways but also for noise barriers at industrial sites and for the upper parts of chimneys at refuse incineration plants, gas turbine power generator plants and various manufacturing plants.