Auxiliary fans are used in hard-rock mines to ventilate development headings, crusher rooms, conveyor transfer points, and underground shops. Depending on the flow requirements and space limitations, single or double stage axial fans with rigid or flexible ducts are used. These fans are noisy, especially when installed in confined environments. Silencer are often omitted for cost reduction purposes or when used, they are not well maintained. This study presents the results of a set of sound level measurements carried out in three underground mines where auxiliary fans are used regularly. Sound levels as high as 98 dB(A) by the workings and 114 dB(A) by the fans were measured in these mines. These levels are quite high even for intermittent noise. Ventilation layouts and best practices used to overcome potential problems related to overexposure to fan noise in underground hard-rock mines are presented. Factors such as fan type, rotational speed, duct diameter, and silencer-duct arrangement, and their effects on noise attenuation are discussed.
