عنوان مقاله [English]
Noise pollution is an important environmental problem which in comparison to other pollutants, the control of environmental noise has been hampered by insufficient knowledge as well as a lack of criteria. Power Plant industries have worldwide substantial progress and noise pollution is one of considerable environmental impacts of various processes of these industries. This cross sectional research aimed to study the sound levels in order to control noise pollution at different sections of Mazandaran Thermal .Power Plant in Iran. Sound pressure level measurements and frequency analysis were performed using .“net” method where the results were compared with ACGIH Threshold Limit Values. The empirical acoustic method used here is based on experiment, which consists of measuring the sound . impulses produced by vibration, propagation and reflection of sound waves. Sound levels at different. locations of Mazandaran Power Plant including steam, synthetic cycle (steam and gas) and official parts. were measured. Environmental impact assessments were also performed at 10 stations near Mazandaran . Power Plant. The location of noise pollution sources and the pause areas of employees were firstly identified and then measurement stations were defined according to ISO 9612.
To estimate the sound levels, the power plant area was divided into equivalent stations by net method. At each station, Sound Pressure Level (SPL), equivalent sound level (Leq) and frequency analysis were performed at one octave band. The total number of stations in steam unit, synthetic cycle unit and lateral installment were 77, 87 and 22, respectively.
Also, nineteen stations were specified in official parts to measure the SPL, Leq and background noise in which ten stations were also considered for environmental noise measurement around Mazandaran Power Plant. The measurements were conducted applying Cell-450 Sound Level Meter where it was calibrated with Cell 110.
It was found that the sound levels were higher in most units where the lowest level of sound was at the official unit. Although some methods such as application of absorptive materials, noise barriers and Active Noise. Control system were suggested to reduce the noise pollution. Electricity generator’s fan and Feed Water. Pump section produce high levels of noise, therefore a silencer and an enclosure were designed . respectively. The amount of noise reduction for enclosure was 38.7 dB while the values of insertion loss . for silencer varied between 11 and 52 dB at different frequencies. Also, environmental noise. measurements around Mazandaran Power Plant as an industrial residential area has revealed that sound . levels were not higher than the admissible standards in Iran.