The Study Of The Prediction Of Noise Impact And Technology Of Noise Control In Urban Complex

Urban complex is the highly aggregated construction group which combined city functions, interplayed and formed value chain. In recent years, urban complex was widely spread in many cities because of the advantages of urban complex like multiple functions, optimization of land resources and prominent social benefits. The concept was introduced in this article, the types and characteristics of noise sources in urban complex were analyzed. The noise impact of cooling tower, lampblack emission fan, refrigerating plant room in urban complex was predicted. According to the results of prediction, the noise control experiments had been done to make the noises of sensitive target outperformed the first category standard of Environmental quality standard for noise> (GB3096-2008) and <Emission standard for community noise>(GB22337-200 8).The research had the following contents and conclusions.(1)The noise sources of urban complex include air conditioning system, lampblack emission system, ventilating system, power distribution system, elevator and entertainment venues. The types and noise characteristics of noise sources in urban complex were analyzed for the noise impact prediction and noise control experiments.(2)This research chose cooling tower, lampblack emission fan and underground garage ventilation system noises of an urban complex which located in class 1 acoustic function zone as the research objects and the hotel in urban complex as the sensitive target. The noise attenuation prediction model of<Technical guidelines for noise impact assessment>(HJ2.4-2009)and area sound source prediction model of energy superposition method were used. According to the types, characteristics and positions of noise sources, different prediction models were used to predict the noise superimposed impact of noise attenuation in horizontal and vertical distance. The results showed that the error value of the two prediction models in the prediction of cooling tower air inlet noise were 3.5dB(A) and 1.5dB(A), the predicted value which took air inlet of cooling tower as the area sound source and used energy superposition method in the prediction was close to the actual value in this research. According to the results of prediction, the required noise reduction of cooling tower, lampblack emission fan and ventilation system air outlet were 23.0dB(A),12.3dB(A) and 3.3dB(A).(3)The noise reduction experiments of cooling tower and lampblack emission fan had been done, the installation of overall sound insulation cover for the cooling tower and the composite silencer in the air inlet and outlet were designed. After the completion of the experiments, the noise value of air inlet was reduced of 23.9dB(A), the noise value of air outlet was reduced of 24.0dB(A), inlet air speed was increased of 1.38m/s, outlet air speed was increased of 1.13m/s, resistance loss was increased of 9.39Pa. Besides, the installation of prevent lampblack composite silencer in the lampblack emission fan outlet was designed. After the completion of the experiments, the noise value of fan was reduced of 16.1dB(A).The noise value in the hotel 5 floor gauging point reduced to 44.1dB (A)from 69.5 dB (A) at night, the noise of each floor were outperformed the first category standard of Environmental quality standard for noise> (GB3096-2008).(4)The vibration and noise from underground service system corollary equipment in urban complex have great affect on the acoustic environment of upstairs in the buildings. This study chose an underground refrigerating plant room in urban complex which located in class 1 acoustic function zone as the research object. The prediction models of technical guidelines were used to analyzes the noise effect to the upstairs in the buildings. According to the analysis, the over-proof of first floor noise mainly affected by air-borne, structure-borne together, the over-proof of second, third floor noise affected by the structure-borne sound of equipment vibration in refrigerating plant room.(5)The vibration isolation structure combined concrete base, damping spring shock absorbers and rubber damping pads were used for the pumps, double rubber damping pads were used for refrigerating machine, the sound absorption materials were hung in the room, the door, windows were replaced by sound insulation door, windows. After the noise, vibration control, the noise value in the first floor reduced to 44.1dB (A)from 69.5 dB (A) at day-time, the noise of each floor were outperformed the first category standard of table.2, table.3 in<Emission standard for community noise>(GB22337-2008).