Noise Control through Active Noise Cancellation Technique in Mines

Abstract

A critical analysis of the exposure of miners to high sound pressure level Noise (>90 dBA) is carried out. The Noise Exposure Index of different machine operators is also observed. And a theoretical solution in the form of a specially designed headphone incorporating Active Noise Cancellation and Band Pass Filter is established. The Noise level was found be above the permissible limits in GDK 10A incline and GDK 10 incline for most of the machinery. At face the noise was within permissible limit of 90dBA only at a distance of 20 m in Tirap mine. The machine producing least noise level among those observed was Mine Riding Car in GDK10A incine and the noise level produced was 74 dBA at 20 m. This very high noise level was hazardous for the miners exposed to them as well as it hampered the speech communication inside the mine.
A solution to it using conventional headphones has failed because of its inefficiency in allowing desirable sounds of person to person communication and the sound of the alarm of the ‘Roof Fall’. This thesis illustrates a design of special headphone incorporating the techniques of ANC and Band Pass Filters for use in mechanized mines which allows all the desirable sound to pass through but filters out the undesired machine noise. The headphone would facilitate efficient speech communication inside the mines.