the sound pressure level was high and noise control was required in those areas. They
proposed some noise control strategies for the noisy sources in mines area.
Pathak et al. [44] described that surface mining noise involved evaluation of sound
power levels of the sources and the determination of different attenuation of the acoustic
wave during propagation. To evaluate the noise sources within a mine the experimental
method developed by them emphasized the determination, of the following:
• Equivalent acoustic centre of different work zones within the mine.
• Ground absorption of sound energy by the type of ground in and around the mines.
• Pit slope attenuation for the prevailing slope conditions within the mine.
• Air absorption of sound during propagation under the predominant meteorological
condition.
Mukhopadhyay and Dey [45] in their comprehensive analysis of noise pollution in
mines described the ‘spherical’ and ‘hemispherical’ propagation of sound. The spherical
propagation sound was expressed as Lw = Lp + 10 log (4π.r2 ) and the hemispherical