Personal noise dosimetry measures the sound exposure associated with a person's movements and activities. A dosimeter is worn during the work, with its microphone positioned close to the hearing zone. The method is intended to represent exposure received by the wearer rather than the sound at a fixed workplace location. The quality of personal sampling depends heavily on the people and working periods selected. A correctly functioning dosimeter can still produce an unhelpful result when the wearer does not represent the group, the sampled duties are atypical or important exposure periods are omitted. Personal sampling is particularly relevant where employees move frequently, work close to changing sources or perform a mixture of noisy and quieter activities. It should be designed as a representative sampling exercise rather than as a collection of convenient individual readings.
The sampling population should be defined before instruments are allocated. The assessor should identify job roles, tasks, equipment, work locations and operating conditions that may create materially different exposure patterns.
Sampling should not be based solely on job title. People with the same title may perform different duties, use different equipment or spend different proportions of the working period in noisy areas. Conversely, employees with different titles may have sufficiently similar exposure patterns to be evaluated together.
Priority is commonly given to employees whose exposure is uncertain, variable or likely to influence a decision about inclusion in protective arrangements. Sampling may also focus on work that previous information identifies as potentially significant.
The person selected should be expected to carry out the work normally. A worker assigned to unusual duties, restricted work or training may not represent colleagues performing the ordinary role. Any departure from the expected work pattern should be recorded.
Contractors and temporary workers should not be overlooked where they perform comparable noisy work or enter noisy operational areas. Their exposure pattern may differ from that of directly employed personnel because of shorter visits, specialist tasks or work during maintenance periods.
A similar exposure group consists of people expected to have sufficiently comparable noise exposure because they undertake similar work under similar conditions. Grouping allows representative samples to inform an assessment of more than the individual wearer.
The group definition should be based on exposure determinants. Relevant determinants include the tasks performed, equipment used, production conditions, location, mobility, task duration and proximity to other sources. A broad departmental label may conceal several distinct exposure patterns.
The assessor should test whether the grouping remains credible after reviewing the results. Substantial differences between samples may indicate ordinary day-to-day variability, but they may also show that the group definition is too broad. Activity records can help explain whether a particular employee spent longer on a noisy task, used different equipment or worked beside another source.
A similar exposure group should not be created merely to reduce sampling effort. Its purpose is to support a defensible inference about people who were not individually sampled. Where the available evidence does not support that inference, the group should be divided or further samples collected.
Grouping should also be reviewed when processes or responsibilities change. A previously coherent group may cease to be comparable after new equipment, revised staffing or altered task allocation.
No universal sample count can represent every workforce or exposure pattern. The required amount of sampling depends on the variability of the work, the size and diversity of the group, the confidence needed for the decision and the consequences of misclassification.
A stable role with repetitive work may require less sampling than a role involving changing locations, intermittent operations and varied task allocation. Where results are tightly grouped and observations confirm comparable work, the evidence may support a group conclusion. Where results differ substantially, additional sampling may be needed to understand the variation.
Sampling should include enough operating conditions to avoid basing a conclusion on a single atypical period. This may involve different work crews, production states, equipment combinations or maintenance conditions where these materially affect exposure.
The assessor should explain why the selected samples are considered representative. A report should not imply statistical confidence that the sampling design does not support. It should state the group represented, the variability observed and any conditions not captured.
Where a decision is close to the comparison value or uncertainty is substantial, further evidence may be appropriate. The need arises from the quality of the inference rather than from an automatic fixed sample count.
The most direct personal sample follows the wearer through the relevant working period. This captures movement between locations, variations in task and exposure from nearby activities.
The run should begin before the relevant exposure starts and continue until the intended period is complete. Delays in fitting the instrument or early removal can omit tasks that make a material contribution.
Breaks and time in quieter areas may form part of the ordinary exposure pattern. They should not automatically be excluded simply because they reduce the average. Equally, time after work has ended should not remain in the dataset without a clear reason.
Where full-period measurement is impracticable, the assessor may sample representative segments and combine them with reliable duration information. This approach requires a clear understanding of the work pattern. A brief measurement of a variable task should not be extrapolated across the remaining period without supporting evidence.
The wearer should be asked at the end of the sample whether the work was typical and whether any unusual event occurred. This information should be considered alongside independent observations rather than accepted as the sole basis for classification.
The microphone should be positioned close to the hearing zone in a stable location. It should not be covered by clothing, obstructed by other protective equipment or placed where it repeatedly contacts a collar, harness or strap.
The wearer should receive a clear briefing before work begins. The briefing should explain the purpose of the measurement, the need to follow normal working practices and the importance of not touching, covering or speaking directly into the microphone.
The dosimeter should not interfere with safe work. The instrument body and cable should be secured so that they do not create an entanglement risk or affect movement. Where other personal protective equipment is worn, placement should be planned so that neither item compromises the other.
The assessor should inspect the position during the sample where practicable. A microphone that was correctly fitted at the start may move during physical work or after clothing and protective equipment are adjusted.
At the end of the run, the condition and position of the equipment should be checked before removal. Any evidence of movement, damage or obstruction should be recorded.
Personal dosimeters are vulnerable to sounds that do not represent ordinary exposure. Direct shouting, blowing, tapping or deliberate presentation of the microphone to a source may create false events. Accidental contact with clothing, tools or equipment can also cause sharp artefacts.
A time history may help identify suspicious events, particularly when the timing can be compared with observations. However, a high or unusual level should not be classified as tampering solely because it appears inconvenient or unexpected.
The assessor should discuss unexplained events with the wearer and compare the trace with task records. Any exclusion should be based on documented evidence. Where the significance cannot be resolved, the uncertainty should be reported or the sample repeated.
Abnormal production events require a different judgement. A breakdown, release of compressed air or unusual vehicle activity may be genuine occupational exposure even when it is not part of routine production. The event should be identified and its relevance to foreseeable work considered.
A sample should not be rejected merely because it produces a high result. Equally, an apparently favourable result should not be accepted where the instrument was covered, removed or worn during duties that did not represent the intended group.
Personal sampling is generally preferable when employees move between areas, work at varying distances from sources or perform tasks with significant changes in level. It follows the person rather than assuming that a fixed location represents the person's exposure.
It is also valuable where several sound sources operate simultaneously and the employee's location relative to them changes. Reconstructing exposure from area measurements may become unreliable where movements and durations cannot be documented accurately.
CoP 3.0 requires representative personal sampling where high mobility, significant sound-level variation or a significant impulse component makes area monitoring generally inappropriate, unless area sampling is demonstrated to produce equivalent results. This requirement applies within the Emirate of Abu Dhabi.
Area measurement may remain suitable for a person stationed at a fixed position where the level is stable and the measurement position is demonstrably equivalent to the hearing zone. It can also complement dosimetry by identifying source levels and explaining sections of a personal time history.
The neighbouring pages /noise-dosimetry and /workplace-noise-assessment address instrument integration and the wider field-survey process, while /noise-exposure-assessment addresses calculation and comparison of the resulting exposure data.
Abu Dhabi's ADOSH-SF requires a competent person to develop and implement a monitoring programme and sampling strategy under CoP 3.0. The strategy must identify employees for inclusion in the hearing-conservation programme and support appropriate hearing-protection selection. Where mobility, variation or impulse noise makes area monitoring generally inappropriate, representative personal sampling is required unless equivalent area results can be demonstrated. These provisions come from CoP 3.0 and apply within the Emirate of Abu Dhabi.
No. Selection should be based on actual tasks, equipment, mobility, duration and uncertainty. A job title alone may not describe the exposure pattern.
Only where the department forms a defensible similar exposure group and the sampled work represents the group's activities and conditions. Broad departments often contain several exposure patterns.
No. The purpose is to record representative work. The wearer should continue normal safe working practices and avoid deliberate interaction with the microphone.
The event should be identified, documented and assessed. It may be a genuine foreseeable exposure, an abnormal event requiring separate reporting or an artefact. It should not be removed automatically.
Only where equivalent results can be demonstrated. A fixed measurement will often fail to follow changes in distance, location and task duration experienced by a mobile employee.