Mine Health and Safety Council Milestones for Occupational Noise
As set out by the Department of Minerals and Energy of the Republic of South Africa
Monitoring Compliance with MHSC Milestone for Occupational Noise
1. Background and Purpose
The Mine Health and Safety Council (MHSC) has established the following milestone for limiting occupational noise exposure and eliminating noise induced hearing loss (NIHL):
"By December 2013, the total noise emitted by all equipment installed in any workplace must not exceed a sound pressure level of 110bD(A) at any location in that workplace"
In order for the Department to monitor industry's progress towards compliance with this milestone, uniform measurement, analysis and reporting procedures will be required as stipulated below.
2. Information to be reported for monitoring compliance
Annual reports must be submitted to the Principal Inspector of Mines, of each relevant region by no later than 31 January of each year. The Operation Details Report Form, attached as Appendix A, must accompany the Noise Milestone Report Form.
The following information must be recorded on the Noise Milestone Report Form, attached as Appendix B:
• Total number of workplaces in each activity area
• Number of workplaces in each activity area where the total noise emission level exceeds 110 dBA
• Number of employees in each activity area exposed to a noise level >110dBA
It is suggested that an inventory of all noise sources in use (types and numbers) and their typical emission level, by activity area and constituent workplaces, be maintained by the mine as part of its risk management system.
3. Noise measurement for workplaces and machinery
The parameter stipulated for quantifying noise emission by the DME Guideline for the Compilation of a Mandatory Code of Practice for an Occupational Health Programme for Noise, ref. DME 16/3/2/4-A3, is equivalent continuous A-weighted sound pressure level, LAeq T, normalised to 8 h as LAeq 8h.
LAeq T should be measured directly with an integrating sound level meter (SLM) that meets the accuracy requirements for at least a Class 2 instrument (given in IEC 61672-1, IEC 61252 and SANS 61672-1) and is fitted with a windscreen type specified by the SLM manufacturer.
The following instrument settings should be used for LAeq T measurements, in accordance with the requirements of SANS 10083/SABS 083:2004 for determining LReq T, a measure that is similar to LAeq T but includes a correction for impulsive noise:
1. A-weighting: On
2. Time weighting: "Fast" or "Impulse" if the noise is impulsive and the
SLM has impulse-integrating capability. If the noise is impulsive but the SLM does not provide for impulse integration, increase the measured LAeq T by 5dBA for moderately impulsive noise (eg. Pneumatic rockdrill) or 12dBA for highly impulsive noise (eg. Compressed air-driven charging-up of blast holes, pneumatic hammering or hammer blows on metal or wood)
3. Sound Incidence: Where applicable, "Frontal" if the microphone is
facing a noise source or "Random" if the noise is non-directional/multi-directional
4. Frequency Filter: Out (Off)
5. Operational Mode: Integrate or Leq
Note:
The following measurement criteria should be applied, in accordance with SANS 10083/SABS 083:2004
• Criterion level/Exposure limit: 85 dBA
• Threshold level/Low threshold limit: 80 dBA
• Energy exchange or doubling rate: 3 dBA
The instrument supplier normally sets the above measurement criteria prior to delivery, but this should be confirmed. For instruments with a facility to alter measurement criteria via onboard software or firmware, measurement criteria should be confirmed or corrected using the instrument's Set-up mode.
The following instrument settings should be used for LAeq T measurements, in accordance with the requirements of SANS 10083/SABS 083:2004 for determining LReq T, a measure that is similar to LAeq T but includes a correction for impulsive noise:
1. Confirm the acoustic sensitivity of the SLM using a sound calibrator that meets the requirements for at least a Class 2 calibrator (given in SANS 60942/SABS-IEC 60942), prior to and after each shift in which measurements have been taken. If the two calibration checks do not coincide to within 1,0 dB, results of the intervening measurements should be discarded and the measurements repeated.
2. For each workplace select at least three microphone positions (more for larger or more variable areas) that are distributed so as to ensure that the highest noise source/s within that working place are identified and the noise level recorded. Microphone positions should be in accordance with the following:
a. Standing Persons: 1.5m above the follow, ground or platform on which the persons stand
b. Seated Persons: 0.9m above chair seat
c. Fixed Workstations: At the position of the employee's most-exposed ear
d. Specific Noise Source: 1m from the source
As far as practicable, the microphone should be positioned at least 1.2m from walls and other large reflective surfaces.
Determine LAeq T in accordance with the requirements of SANS 10083/SABS 083:2004 for determining LReq T, a measure that is similar to LAeq T but includes a correction for impulsive noise. Measure for a representative time at each selected microphone position (minimum of three). For steady noise, a measurement time of 1 minute is adequate. Where noise varies or is cyclical, measurement time should be sufficient to capture variations in level and include a reasonable number of work task cycles to ensure representative results.
If impulsive noise is present and measurements were made with a basic integrating sound level meter that does not incorporate a time-weighting function, and estimated impulse correction factor can be applied. Increase the measured LAeq T value by 5dBA for moderately impulsive noise (e.g. pneumatic rockdrill) or 12dBA for highly impulsive noise (e.g. compressed air driven charging-up of blast holes, pneumatic hammering or hammer blows on metal or wood). Alternatively, if an integrating sound level meter capable of L-time-weighting (Impulse) and S-time-weighting (Slow) is used, a derived impulse correction factor can be applied. The derived impulse correction factor is the difference between values obtained for maximum A-weighted sound pressure level (measured in SPL mode, as opposed to Integrating or Leq mode) using I-time weighting and S-time weighting, and should be added to the value measured for LAeq T in Integrating or Leq mode.
The details of measurement procedures should be documented so as to ensure uniformity, thereby allowing meaningful comparisons of present and previous results. This is best achieved by using a detailed sketch (or similar) to define microphone positions and characterise workplace operating conditions, e.g. number and types of machines in use.
Since the primary purpose of measurements is to enable an assessment of compliance with the MHSC milestone for noise emission, only the maximum observed LAeq T for each workplace is required. However, results for individual machines and microphone positions should also be recorded to assist in the identification of machinery that contributes significantly to workplace emission levels.
Monitoring Compliance with MHSC Milestone for Occupational Noise
1. Background and Purpose
The Mine Health and Safety Council (MHSC) has established the following milestone for limiting occupational noise exposure and eliminating noise induced hearing loss (NIHL):
"By December 2013, the total noise emitted by all equipment installed in any workplace must not exceed a sound pressure level of 110bD(A) at any location in that workplace"
In order for the Department to monitor industry's progress towards compliance with this milestone, uniform measurement, analysis and reporting procedures will be required as stipulated below.
2. Information to be reported for monitoring compliance
Annual reports must be submitted to the Principal Inspector of Mines, of each relevant region by no later than 31 January of each year. The Operation Details Report Form, attached as Appendix A, must accompany the Noise Milestone Report Form.
The following information must be recorded on the Noise Milestone Report Form, attached as Appendix B:
• Total number of workplaces in each activity area
• Number of workplaces in each activity area where the total noise emission level exceeds 110 dBA
• Number of employees in each activity area exposed to a noise level >110dBA
It is suggested that an inventory of all noise sources in use (types and numbers) and their typical emission level, by activity area and constituent workplaces, be maintained by the mine as part of its risk management system.
3. Noise measurement for workplaces and machinery
Measurement Criteria
The parameter stipulated for quantifying noise emission by the DME Guideline for the Compilation of a Mandatory Code of Practice for an Occupational Health Programme for Noise, ref. DME 16/3/2/4-A3, is equivalent continuous A-weighted sound pressure level, LAeq T, normalised to 8 h as LAeq 8h.
LAeq T should be measured directly with an integrating sound level meter (SLM) that meets the accuracy requirements for at least a Class 2 instrument (given in IEC 61672-1, IEC 61252 and SANS 61672-1) and is fitted with a windscreen type specified by the SLM manufacturer.
Instrument Settings
The following instrument settings should be used for LAeq T measurements, in accordance with the requirements of SANS 10083/SABS 083:2004 for determining LReq T, a measure that is similar to LAeq T but includes a correction for impulsive noise:
1. A-weighting: On
2. Time weighting: "Fast" or "Impulse" if the noise is impulsive and the
SLM has impulse-integrating capability. If the noise is impulsive but the SLM does not provide for impulse integration, increase the measured LAeq T by 5dBA for moderately impulsive noise (eg. Pneumatic rockdrill) or 12dBA for highly impulsive noise (eg. Compressed air-driven charging-up of blast holes, pneumatic hammering or hammer blows on metal or wood)
3. Sound Incidence: Where applicable, "Frontal" if the microphone is
facing a noise source or "Random" if the noise is non-directional/multi-directional
4. Frequency Filter: Out (Off)
5. Operational Mode: Integrate or Leq
Note:
The following measurement criteria should be applied, in accordance with SANS 10083/SABS 083:2004
• Criterion level/Exposure limit: 85 dBA
• Threshold level/Low threshold limit: 80 dBA
• Energy exchange or doubling rate: 3 dBA
The instrument supplier normally sets the above measurement criteria prior to delivery, but this should be confirmed. For instruments with a facility to alter measurement criteria via onboard software or firmware, measurement criteria should be confirmed or corrected using the instrument's Set-up mode.
General Procedures
The following instrument settings should be used for LAeq T measurements, in accordance with the requirements of SANS 10083/SABS 083:2004 for determining LReq T, a measure that is similar to LAeq T but includes a correction for impulsive noise:
1. Confirm the acoustic sensitivity of the SLM using a sound calibrator that meets the requirements for at least a Class 2 calibrator (given in SANS 60942/SABS-IEC 60942), prior to and after each shift in which measurements have been taken. If the two calibration checks do not coincide to within 1,0 dB, results of the intervening measurements should be discarded and the measurements repeated.
2. For each workplace select at least three microphone positions (more for larger or more variable areas) that are distributed so as to ensure that the highest noise source/s within that working place are identified and the noise level recorded. Microphone positions should be in accordance with the following:
a. Standing Persons: 1.5m above the follow, ground or platform on which the persons stand
b. Seated Persons: 0.9m above chair seat
c. Fixed Workstations: At the position of the employee's most-exposed ear
d. Specific Noise Source: 1m from the source
As far as practicable, the microphone should be positioned at least 1.2m from walls and other large reflective surfaces.
Measurement Procedures
Determine LAeq T in accordance with the requirements of SANS 10083/SABS 083:2004 for determining LReq T, a measure that is similar to LAeq T but includes a correction for impulsive noise. Measure for a representative time at each selected microphone position (minimum of three). For steady noise, a measurement time of 1 minute is adequate. Where noise varies or is cyclical, measurement time should be sufficient to capture variations in level and include a reasonable number of work task cycles to ensure representative results.
If impulsive noise is present and measurements were made with a basic integrating sound level meter that does not incorporate a time-weighting function, and estimated impulse correction factor can be applied. Increase the measured LAeq T value by 5dBA for moderately impulsive noise (e.g. pneumatic rockdrill) or 12dBA for highly impulsive noise (e.g. compressed air driven charging-up of blast holes, pneumatic hammering or hammer blows on metal or wood). Alternatively, if an integrating sound level meter capable of L-time-weighting (Impulse) and S-time-weighting (Slow) is used, a derived impulse correction factor can be applied. The derived impulse correction factor is the difference between values obtained for maximum A-weighted sound pressure level (measured in SPL mode, as opposed to Integrating or Leq mode) using I-time weighting and S-time weighting, and should be added to the value measured for LAeq T in Integrating or Leq mode.
Recording measurement results
The details of measurement procedures should be documented so as to ensure uniformity, thereby allowing meaningful comparisons of present and previous results. This is best achieved by using a detailed sketch (or similar) to define microphone positions and characterise workplace operating conditions, e.g. number and types of machines in use.
Since the primary purpose of measurements is to enable an assessment of compliance with the MHSC milestone for noise emission, only the maximum observed LAeq T for each workplace is required. However, results for individual machines and microphone positions should also be recorded to assist in the identification of machinery that contributes significantly to workplace emission levels.
