Iran Occupational Health

  Background and aims: In the steel industry, air blowers used to supply compressed air are considered as sources of annoying noise . This study aims to design an acoustic room chamber in order to control the noise level of the air blower.

  Methods: Measuring of the noise level along with frequency analysis was performed by using sound level meter, model ofCASELLA-Cell.450 . Dosimetery was performed in order to assess the worker’s exposure using the dosimeter model TES-1345. Linear sound power level of machine was calculated based on ISO-3746. Distribution of noise emission of the source was shown in form of workroom noise maps using Surfer software. Acoustic analysis of workroom was performed based on sound absorption characteristic of internal surfaces. In order tocontrol noise level, an enclosure along with condensed sandwich panels was designed for blower and finally, the effect of this intervention was estimated.

  Results: The results showed that the total sound pressure level of the air blower was 95.4dB (Lin) in which the dominant frequency was 2000 Hz. Moreover, sound power level of the air blower in the dominant frequency was 102.94dB (Lin). The effective absorption surface of workroom was estimated equal to 0.082 and the average occupational noise exposure level based on noise dose was equal to 230%.By designing the enclosure along with the steel and fiberglass as a primary insulation layer and punched steel sheet as absorption layer on internal surfaces, the actual transmission loss in the dominant frequency, by taking into account the 0.001 of leakage was estimated as 30dB.

    Conclusion : gearbox and compressor weretwo main sourcesof air blower noisedue to the spiral gearing wheels spinning rotor gearbox parts and the interaction between the rotary and fixed blades and the movement of air through the compressor. Following the enclosure design,the noise dose received by worker was reduced to less than 20 percent.