Automated Noise Dose Exposure Recording
System -

Netshield initiative





Purpose of noise Measurement

• The fundamental purpose of noise measurements is to identify and assess the extent of noise- related risks, including risk of noise-induced hearing loss (NIHL) and safety risks caused by interference with communication.

• Can assist in selecting the most suitable hearing protection devices (HPD) for exposed employees.

• Employee exposure levels are measured, usually by means of personal noise dosimetry, to monitor risks.


Compliance with Regulatory Requirements

In addition to the purposes outlined above, noise measurements arenecessary to satisfy various legal and regulatory requirements. 

• The Mine Health and Safety Act (MHSA) requires the employer to identify hazards [MHSA 11.(1)(a)], assess risks [11.(1)(b)], implement measures to eliminate, control or minimise them [11.(2) and (3)], and monitor those risks that still remain [11.(4)(a) and 12].

• Exposure levels greater than 85 dBA pose a significant risk of NIHL and oblige the employer to implement a hearing conservation programme (DME 20031, 8 and 8.3.1). This shouldinclude the implementation and evaluation of control measures along with risk monitoring, indicating a need for accurate and representative noise measurements.


Departement of Minerals and Energy



In order for the Department to monitor industry's progress towards compliance with this COP, uniform measurement, analysis and reporting procedures are required as listed in DME 16/3/2/4- A3 page 32-76

The COP of Anglo Platinum ref: COP OH1.3 is a good reference to comply to the DME requirements. The NXDOSI system provides information reports in formats to support compliance with the requirements

Annual reports must be submitted to the Principal Inspector of Mines

This guideline assists employers with the establishment of an Occupational Hearing Conservation programme, but does not stipulate specific requirements for specific circumstances. It sets out a basic system for managing risk to health. The first component of any management system is finding out what the situation is, the second is deciding what to do about it, and the third is to implement appropriate controls.

“In accordance with section 9(2) of the MHSA an employer must prepare and implement a COP on any matter affecting the health and safety of employees and other persons who may be directly affected by activities at the mine if the Chief Inspector of Mines requires it. These COPs must comply with any relevant guidelines issued by the Chief Inspector of Mines (section 9(3)).” DME 16/3/2/4-A3 page 3(2.1)

“As far as employees are concerned, section 22 places a number of obligations on employees, including that they must take reasonable care to protect their own health and safety and the health and safety of other persons who may be affected by their conduct. Where a failure by an employee to comply with a COP would also constitute a breach of the employee’s duties in terms of section 22 (or a breach of section 84, 86(1) or 88), the employee could be criminally charged for such breach. As is the case with employers, the inspectorate could issue instructions to employees in terms of section 54 and failure to comply with such an instruction constitutes a criminal offence.” DME 16/3/2/4-A3 page 4 (2.4)


Requirements for noise exposure measurements

The general requirements and guidelines for noise measurement provided are provided in DME 16/3/2/4-A3 section 3.5

Analysis of noise exposure measurement results


Classification of observed noise exposure levels

Mean TWA (dB)
Exposure rating factor and characterisation
of risk
=82   0: Insignificant risk
83-85   1: Potential risk
86-90   2: Moderate risk
91-95   3: Significant risk
96-105   4: Unacceptable risk
=106   5: Extreme risk


DME reporting requirements for occupational noise.

The DME requires annual reports on the results of personal noise monitoring that identifies occupations in which employees are exposed to dangerous noise, the number of employees exposed, and the logarithmic average sound pressure level. The DME must also monitor the mining industry’s progress towards compliance with Mine Health and Safety Council milestones for occupational noise, which will require reports that include at least the following information:

• an inventory of all noisy equipment in use and typical emission level for each activity area and workplace;

• total noise emission (LAeq) during full-scale operations for each activity area and workplace, and

• a list of workplaces in each activity area where total noise emission exceeds 110 dBA.


 Departement of Minerals and Energy

Occupational health program



Hearing conservation programme

Any hearing conservation programme in accordance with this standard should consist of the following:

• For new installations, adjudicate the layout plans and proposed equipment complement, in order to predict by calculation the 8 h rating level (LReq,8h) in the proposed work environment.

• When the existing installation is to be changed, adjudicate the layout plans and proposed equipment complement in order to predict by calculation the 8 h rating level (LReq,8h) in the proposed work environment.

• Assessment of the 8 h rating level (LReq,8h) in the existing work environment.

• The obligatory introduction of alternative engineering or administrative procedures and layouts of the workplace to limit the noise exposure of the employees.

• Where improvement to limit the 8 h rating level (LReq,8h) to below 85 dBA is not possible, demarcation of noise zones.

• The issue, free of charge, of certified hearing protection equipment to the employees in the noise zones.

• Introduction of the wearing of certified hearing protection equipment.

• Introduction of audiometric assessment.


The main objectives of Noise Monitoring are:

• To assess the ambient Noise Level status in and specific environment

• To compare measured Noise Levels against ambient Noise standards and to assess the extent of violation.

• To identify the significant contributors of Noise Level so as to take overall decision for mitigation at the source itself.

• To identify significant factors and its individual impact and to suggest alternative measures.

SEL – SOUND EXPOSURE LEVEL. This is the notional sound pressure level which, if maintained constant over one second, delivers the same amount of acoustic energy at some point as the timevarying sound pressure level would deliver at the same point over its entire duration. SPL – SOUND PRESSURE LEVEL. Sound intensity level for any given instance. LEQ - This is where the Leq noise or equivalent continuous noise level meter comes in. This meter faithfully follow all the fluctuations, stores them in it's short-term memory and at the end of the measurement calculates an 'average' value called the Leq value. When we say average, this is not a simple arithmetic average because we are measuring in decibels which logarithmic values. So our meter converts the dB values to 'real numbers', adds them all up then divides by the number of samples and finally converts this true energy average back to dBs.


A Weighting A standard weighting of the audible frequencies designed to reflect the response of the human ear to noise
C Weighting A standard weighting of the audible frequencies used for the measurement of Peak Sound Pressure level.
Z Weighting Z weighting is a flat frequency response between 10Hz and 20kHz ±1.5dB excluding microphone response.
Acoustic Calibratorl

An instrument that provides a reference noise source that is used to calibrate and check the performance of a
Sound Level Meter.

Data Logging Measurements can be stored in the Sound Level Meter for download to a PC
dB(A) Decibels A weighted
dB(C) Decibels C Weighted
dB(Z) Decibels Z weighted
Decibel (dB) The units of sound level and noise exposure measurement
% Dose The noise exposure expressed as a percentage (%) of a fixed level for 8 hours
LAS Sound level with 'A' Frequency weighting and Slow Time weighting
LCS Sound level with 'C' Frequency weighting and Slow Time weighting


Noise rating limits

• The 8 h rating level (LReq,8h) as determined, should not be equal to or exceed 85 dBA. If this limit is reached or exceeded, the area should be identified as a noise zone and hearing conservation measures are required.

• Hearing conservation measures as described in clause 5 are not adequate where the rating level (LReqr,8h) equals or exceeds 130 dBA, and additional advice from an expert should be obtained.


*LAeq, T /
LReq, T/
TWA8h (dBA)

Exposure Classification According To:                  
Occupational Hygiene Regulations

Emission/Exposure Classification Factor (ECF), Level of
Significance and Required Action

< 82 -

0 Insignificant risk of NIHL.
No action required.



1 Potential risk of NIHL
Monitoremission and exposurelevels for upward trends.

86-90 B 2 Moderaterisk of NIHL.

Intervene,Re-assess andMonitor.

91-95  B  

3 Significant risk
Priority intervention.Re-assess andMonitor

96-105 B  

4 Unacceptablerisk.
Immediateintervention.Re-assess andMonitor

= 106 A  

5 Extreme risk.
Urgent intervention.Re-assess andMonitor.



The NXDOSI-meter product and subsystem System:

• provides quantified noise exposure recordings for analysis of noise levels that could have an impact on long term hearing

• part of the Cap Lamp assembly

• recordings are automatically wirelessly downloaded after a shift and stored in a database for processing and reporting.

• A visible red led light signal in the cap lamp is activated to warn the employee when the noise exposure dose is exceeded

• complies with applicable intrinsic safety standards and certifications

• custom configurable entry level product analyses and records dataset for downloading

• where the enhanced unit is fitted with pressure and humidity sensors used to increase the quality and accuracy of the recordings



• The NXDOSI System is a hardhat mountable assembly, integrated as part of the Cap Lamp and powered from the Cap Lamp battery

• this integration ensures that users always wear the system

• the automatic download of recorded samples to a database occurs when the unit moves into close proximity of the wireless base

• this automatic process eliminates additional resources to issue the



Cap Lamp Integration

Consists of the existing SCHAUENBURG GDI VIROCAP

• Retrofitted with a cover to house all the electronics and components of the system

• Complies with applicable safety and intrinsic standards


Technical Specifications

1 measurable channels 2 (Dual) Channel, Fixed A with either C or Z-weighted option
2 Dynamic Range (dB)measurement mange RMS Range 70 to 140dB and Peak Range 110 to 143dB
3 Frequency weightings ‘A ’ or ‘C’ for all RMS measurements or ‘Z ’ for Peak Sound Pressure
4 Time weightings FAST(125ms) or SLOW(1000ms)
5 Exchange rate (Q dB) 3, 4 or 5 for each dosimeter
6 Criterion level (dB) Any level between 70 and 90 in 1 dB steps
7 Criterion Time (hrs) 8, 12, 16 or 18
8 Memory storage (results) minimum 10 hours storage maximum of 24 hours
9 Measurement Functions SPL, Lavg/Leq, TWA, Max, Min, Peak C or Z, Exposure Dose, Run Time and Battery Voltage Level
10 Storage interval 1 Minute or 1 Second
11 Real time clock EPOCH time sync at start-up, 1second increments
12 Fixing method to worker Clips provided for hard hat mounting
13 Microphone protection Lockable foam windscreen to protect microphone
14 Software SQL Database with download and analysis software
15 Output Zigbee wireless communication
16 Environmental Operating Temperature Range: -10° C to 50° C Storage Temperature Range: -25° C to 60° C Humidity Range: 0 to 95% Non-Condensing
17 Indicators Hi-bright LED’s indication : System status, recording status on/off and battery voltage
18 Weight (g) < 100 g
19 Case moulding High impact ABS plastic moulding
20 Battery pack Standard Schauenburg Headlamp battery pack
21 Battery life (hr) 10 hours minimum
22 Identification of multiple units Unique 64 bit serial number
23 Microphone capsule Removable ½” type 2 compliant device can be calibrated with any standard acoustic calibrator using ½” diameter cavity
24 Calibration method Automatic recognition and calibration with SANS 60942 certified calibrator
25 Intrinsic Safety EX ia I/IIC T4
26 Accuracy standards IEC 61252 (NMISA verified)


Basic Elements

Typical noise dosimeter building blocks:

When sound deflects the microphone’s pressure-sensitive diaphragm an electrical signal is sent to the preamplifier, which boosts the signal to a usable level before sending it to the frequency weighting filters. The filtered from the preamplifier, which corresponds with the pressure of the sound, is proportional to the sound’s instantaneous power. The measurements are recorded and the results can be transferred to computer for further analysis, permanent storage and generating reports.



Device Enclosure


NXDOSI Reporter Software



  •   Automatic Wireless Download and Configuration when in proximity of the base station

• Stored data is automatically downloaded to a database

• Preselected configuration is uploaded to the unit

• Unit is calibrated according to parameter control options, complying with occupational monitoring equipment legislation

• Onboard storage of all the relevant calibration information


  •   Data and Exposure Analysis

• Exposure levels can be colour-coded by a simple ‘traffic light’ type system

• Clear and easy selection of individuals, groups, sections or locations

• User/management preselected noise levels, compliant with local legislation, can be defined

• Visual tabular and graphical displays and reporting of downloaded Data


  •   Easily Generate Reports

• Reports can be generated in multiple formats (eg: .pdf, .jpg, or .csv) allowing them to be shared and viewed easily

• Report data can be exported to other applications

• Integral report wizard allows reported parameters to be selected as required

• Report settings are retained

• User/management notes can be added to data, which appear on reports are required



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