Development of the Product-type Active Soft Edge Noise Barrier Keizo Ohnishi 1 , Takashi Saito 2 , Susumu Teranishi 2 Yoshiharu Namikawa 3 , Teiji Mori 3 , Kenji Kimura 4 , Katsumi Uesaka 5 1 Takasago R&D Center, Mitsubishi Heavy Industries Ltd. 2-1-1 Shinhama, Arai-cho, Takasago, Hyogo Pref. 676-8686 Japan 2 Kobe Shipyard & Machinery Works, Mitsubishi Heavy Industries Ltd. 1-1-1 Wadasaki-cho, Hyogo-ku, Kobe, Hyogo Pref. 652-8585 Japan 3 National Institute for Land and Infrastructure Management, Ministry of Land, Infrastructure and Transport, Asahi 1, Tsukuba, Ibaraki Pref. 305-0804 Japan 4 Hyogo National Highway Office, Ministry of Land, Infrastructure and Transport, Chuo-ku, Kobe, Hyogo Pref. 650-0042 Japan 5 Fukushima Office of River and National Highway, Ministry of Land, Infrastructure and Transport, Fukushima, Fukushima Pref. 960-8584 Japan Abstract Recently there are great needs to reduce road traffic noise. They use several noise countermeasures to reduce it; e.g. drainage asphalt pavement, noise barrier et al. Especially noise barriers, several new types of them were developed as passive control methods; e.g. absorbing materials on the edge of the barrier, some particular shapes on the edge et al. 1)2)3) However absorbing type is effective over 500Hz or particular shape type usually has big size. In case drainage asphalt pavement is installed on the road, the superior frequency of noise spectrum will be shifted 850Hz or lower. After the noise barrier, the superior frequency of noise spectrum will be shifted 500Hz or lower, absorbing type noise barrier is not effective on that frequency range. Also we have some restriction to set the big size noise barrier on the public road. We developed the new type noise barrier with the active controlled device on the edge of it. The devices minimize the surface sound pressure by active noise control with wide frequency range. The attenuation of this new concept compact noise barrier is over 5dB by average superior to uniform-type one at the same height by outdoor noise test using 20m long barrier. 1. Introduction Needs for high performance of noise barriers to be the countermeasure against road traffic noise have been ever increasing. Our team has been working to develop Active Soft Edge Noise Barrier (hereafter referred to as ASE Noise Barrier) 4)5) which can reduce diffracted noise of the barrier with a compact size by applying the active noise control technique. It has been verified that the barrier can furthermore track a traveling noise source and demonstrate its efficiency. 6) We have developed Product-type ASE Noise Barrier with a rationalized structure and more practicality in comparison with the prototype ASE Noise Barrier. 2. Configuration of Product-type ASE Noise Barrier Figure 1 shows the configuration of Product-type ASE Noise Barrier that consists of a microphone, a loud speaker, absorptive materials, ASE cell covered by weather resistant sheet, a microphone amplifier, a control circuit and a power amplifier. It reduces the diffracted noise from the barrier top by minimizing the sound pressure on the surface of the ASE sell. Cross-section of Product-type ASE is shown Fig. 2. It was changed cylindrical (prototype) to inverted triangle; structure of Product-type was made simple by the inverted triangle cross-section and its frame being bent Fig. 1 Configuration of Product-type ASE Noise Barrier Tu2.F.5 II - 1041