Document Type : Original Article

Authors

• Farhad Forouharmajd ¹
• Parvin Nassiri ²
• Mohammad Reza Monazzam ²

¹ Department of Occupational Health Engineering, School of Public Health, Isfahan University of Medical Sciences, Isfahan; Tehran University of Medical Sciences, Tehran, Iran

² Department of Occupational Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran

Abstract

Aims: The aim of this study is to find manners of noise abatement to reach to its allowable values by which the noise caused by compressors can be reduced, and if use of enclosure is an effective alternative. Materials and Methods: In the study, analysis of noise caused by the compressor and how distribution of sound frequencies with and without the use of enclosure was done, and then compared with standard values to help choose the best absorber material. This method is in accordance with the in situ assessment techniques for noise generated by different sources. A second order analyzer was use to study the recorded sound pressure level (SPL) values, and to demonstrate which frequencies can be more important in designing the enclosure. A sheet metal was used for enclosing the compressor, and this was lined with an absorber material to achieve a better sound reduction. SPL levels, before and after the enclosure of the compressor with the sheet material, were measured and compared. Results: There was a reduction in the level of noise produced for all frequencies due to use of the enclosure, a difference of 10 to 50 dB of reduction was recorded for all the frequencies. For higher frequencies in the range of 500 Hz to 4000 H, the SPL showed a similar reduction. A reduction of 50 dB in the produced noise below the standard was seen for the frequency of 63.5 Hz in octave band frequencies. There was also a permissible limit for higher frequencies of noise produced by the compressor, but with a gap of 10 dB of its standard limit at the frequency of 500 Hz. Conclusions: An overall noise reduction by 25 dB with the use of mineral wool as an extra liner on the inside of the enclosure, suggests that the effectiveness of the enclosure can be increased by using such absorber materials.

Keywords

• Compressor
• enclosure
• frequency analysis
• noise pollution