| ObjectiveTo control noise risk factors, and determine reasonable an effective control measures and suggestions to reduce the harm for workers, an investigation was carried for understanding the basic situation of noise pollution and noise protection and management in iron and steel industry more clearly, with the occupational environmental noise dose and individual absorbed dose level was measured. So that it was more reasonable and feasible for selecting earplugs scientifically and personally with studying on the spectrum characteristics of earplugs.Methods1. Monitoring and analysis of occupational environmental noise level: Wuhan Iron and Steel Corporation was selected as typical study object, then the exploration drawing was made for the area of the workplace, space, technology division, noise equipment layout of cold-rolled three main plant and bar plant of large factory field. The survey schedule table was developed for number of observers, work route, way, time, etc. Noise measured in line with GBZ/T189.8-2007. According to GBZ2.2-2007, measurement is set to A meter power, the "S"(slow) file take the equivalent sound level LAeq in Noise monitoring sound level meter.2. Measurement and evaluation of individual absorbed dose level:Healthy physical chart of workers was developed according to GBZ188-2006. Pure tone air conduction audibility threshold test was carried out. Occupational hearing loss was diagnosed determined in line on GBZ49-2007, WHOGB249-2002.3. Scientific selection of earplugs:The deadening earplugs were chosen according to the method of acoustic attenuation measurement in GB-T7584.1-2004. REAT testing was used, hearing threshold attenuation was made through l/3octave bands of narrow band noise(center frequency0.125kHz,0.25kHz,0.5kHz,1kHz,2kHz,3kHz,4kHz,6kHz,8kHz), the Analysis of variance was used to inspect the differences of earplug attenuations. Appropriate earplugs were chosen for each noise workers according to GB-T7584.2-1999.Results1. There were55monitoring data in noise environment, The point which Noise intensity was greater than or equal to85dB (A) were31, The percentage was56.36. Noise intensity focused on within the range of70-75dB (A) in operation room, The excessive number of15, which is93.75%. The spectrums of sound pressure level were differences in Workshop in different positions.2. The difference of hearing loss between different working age groups was significant(x2=175.69,p<0.01) in1697noise workers; the incidence of hearing loss showed a increasing tendency with the working age<5,10-20,20-30,5-10,30-40and>40of noise exposure. The severity was related with gender(x2=30.879,p<0.01).3. The analyses indicated that there were statistical difference among the eighteen HPDs cross the nine frequencies (P<0.01). Seventeen types of earplugs met with the BS EN352-2-2002standard, one earplugs made in china did not meet with the standards except8kHz. Eighteen earplugs was compared with Our country’s standard (GB5893.1-86),61%of earplugs up to standard, the acoustic attenuation values of all earplugs in class A, met standard; In class B, there were four earplugs reach the standard except the attenuation values on4kHz; Earplug in class C did not comply with the standard except0.5kHz; Class D earplug was substandard. There was no statistical significance of the rate of reach the standard between domestic earplugs and importing earplugs (P>0.05).Conclusions1. Operating point noise damage mainly between80-94db (A) in this Iron and steel enterprises, the harm of noise was still serious. The effect of Soundproof in operation room can not meet the national health standard health standard for design of industrial enterprises. The spectrums of sound pressure level were differences in Workshop in different positions.2. There were greater incidence of hearing loss, mostly high frequency damage, the general trend was existed, and hearing loss rate was rising along with the extension of the Length of service. The incidence and severity of hearing loss related with working age and gender.3. The earplugs noise reduction values varied with frequency, because of the good noise reduction effect, and the material and shape of earplugs may be the main factors affecting the acoustic attenuation values. Further research may be demanded, which due to the less-than-ideal rate of reach the standard.4. Earplugs in class A could be recommended to use in this noise environment.5. A suggestion that our country should increase the range of frequency in earplug evaluation criterion was putted forward. |
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