Estimation Method for Acoustic Performance of Noise Reducing Devices on the Noise Barrier Consitering the Source Characteristics

Noise barriers have been the most common method for abating the road traffic noise to the roadside residents, and the noise reducing device(NRD), generally called 'noise reducer' in Koreahas been installed in many cases for more shielding effect of noise barriers. TheNRD is an acoustic device which installed on the top of noise barriers for the purpose of reducing the diffracted soundcaused by noise barriers. It was studied and suggested by Dr.Fujiwara(Japanese) for cutting down the acoustic edge potential of a noise barrier in the early 1990's and introduced in Korea at the end of 1990's. Since, many kinds of products have been developed and installed on railway noise barriers as well as road barriers in Korea. The acoustic performance of NRD is depended on the frequency spectrum of noise source. But because of installing without any considerations about the source spectrum, the performance of NRDs could not be showed as designer's intention in real situations. In this study, an estimation method which reflected the source spectra has been considered and suggested for appropriate installation of NRD's and for 14 NRD samples estimated and compared their performance with different source spectra.