Auditory communication in the mining industry. Final report on CEC Contract 6245-11/8/019

The investigation considered non-verbal and spoken communication in the mining industry.A survey was carried out to determine the range of hearing abilities of the workers at a colliery. The noise levels at the workstations in one working district of a colliery were recorded to provide information on the sound environment in which communication had to take place.A computerised system for evaluating warning signals was developed which allowed for the masking effects of background noise and the hearing abilities of mineworkers. The system was applied to typical sound signals used in the mining industry, Bells used for rope haulage signalling were found to be adequate but electronic pre-start warning signals did not meet the criterion adopted for minimum effective signal levels.Recommendations for evaluating signals with standard equipment were made. One-third octave measurements of background noise were preferred for the assessment of masking and minimum effective signal levels for quiet conditions were suggested.Measurements of sound propagation in mining conditions were made and the Inverse Square Law shown to hold at distances up to 30 m along mine roadways. This result was used to determine the effective ranges of sound signals.A variety of speech interference indices were assessed in relation to noises typical of the mining industry. The Four Octave Preferred Speech Interference Level and the Articulation Index were shown to be the best predictors of interference with direct spoken communication.Preliminary investigations of coalface tannoy performance were made and it was shown that such tannoys were likely to be ineffective when used in some typical background noises.Noise conditions in a colliery generating house were investigated and specifications produced for a headset-based radio communications system. The degree of attenuat-ion from the headset muff and the extent of microphone noise-cancelling required were calculated to ensure that adequate communication would be possible without producing noise levels or speech signals at the ear which could damage the worker’s hearing. “”