| 英文摘要 |
The study comprised three objectives, the first objective is to propose the measurement guideline and index of low frequency traffic noise, and try to find the pattern of the low frequency traffic noise. The second objective is to provide help with field survey of some construction sites and measure low frequency noise in such sites then offered the guidance report in accordance with the noise state. The third objective is holding a meeting which invited the persons from construction society and competent authorities.
The measurement of low frequency traffic noise were implemented in 28 spots such as expressways, highways, ordinary roads, high speed trains(THSRC), ordinary trains and mass rapid transit trains(MRT). For the 20-200Hz frequency noise, the hourly-equivalent energynoise were among 50-60dB(A). The noise under the expressway and highways were higher than the noise beside the mentioned ways, in spite of the barriers. The cause might be the different type of flyover and joints of the ways. According to the frequency analysis results, there were no distinguished main frequency patterns among the roads. Only the roads where there were more trucks, the 63Hz and 80 Hz frequency were a little peak. Among the track system, because there is open area in the flyover of the MRT system, the noise will transmit through it, the noise under the MRT track is high than the noise beside the track, as well as the ordinary trains. The noise from the THSRC under the track was lower than the noise beside the tracks. And we found that the barriers were effective. For the hourly-equivalent energynoise beside the track, the MRT were 51.6-69.8dB(A), the ordinary trains were 58.2-70dB(A), the THSRC were 59.2-69.3dB(A). The noise from the tunnel of THSRC was higher in low frequency and infrasound. Compared with the threshold of rattling fittings of Japan, some spots of THSRC was over in 31.5Hz. The others over threshold situation were in infrasound. For the index of track system, we suggested the average Lmax noise of one hour passing trains. For the index of roads system, the hourly-equivalent energyenergy noise was suggested or if there will be many trucks, the average passing Lmax noise is also recommended.
In field survey of ten construction sites, the experts were invited to provide noise improving suggestion in situ and explain the low frequency limit in Noise Control Standards of construction sites. Twenty-six spots were measured in front of several buildings or machines to evaluate the noise to the buildings. The sources were such as excavators, cement mix trucks and generators. The suggestions were such as prevent the noise from pointing to sensitive areas and maintain the machines frequently.
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