Personal Noise Dosimetry
Personal noise dosimetry measures an individual worker's changing sound exposure throughout representative tasks, movements and work periods — so daily personal exposure can be quantified and interpreted against UK Control of Noise at Work Regulations 2005 action and limit values.
Hearing zone
Microphone position
LEX,8h
Daily personal exposure
CNWR 2005
UK regulatory context
Worker-worn shift dosimetry
Representative exposure across real work activities
What it is
What is personal noise dosimetry?
A personal noise dosimeter is a small, body-worn instrument attached to the employee's clothing — typically on the shoulder — with the microphone positioned in the hearing zone close to the ear. The dosimeter records sound exposure continuously over the agreed monitoring period rather than capturing a single instantaneous reading.
Because the microphone moves with the worker, dosimetry captures exposure across the actual tasks, locations and movements that make up the shift. This is especially valuable for mobile or multi-task workers whose noise exposure cannot be fairly characterised by fixed-position sound-level measurements alone.
A dosimeter records exposure data — it does not replace observation, activity records or professional interpretation. The reliability of the result depends just as much on what was happening during the shift as on the instrument itself, which is why dosimetry sits within a wider workplace noise monitoring and noise exposure assessment programme. For an educational overview of the method itself, see what is personal noise dosimetry.
When it fits
When personal dosimetry is appropriate
Dosimetry is most useful where exposure varies — by task, by location, by shift or by individual. It is not automatically required for every workplace noise assessment.
- Workers moving between multiple areas during a shift
- Changing tasks throughout the working day
- Intermittent high-noise activities such as grinding or impact work
- Mobile maintenance and engineering teams
- Warehouse and logistics duties with varied movement
- Construction work across multiple zones
- Variable production cycles and batch operations
- Exposure to several machinery sources during one shift
- Tasks that cannot be characterised by fixed measurements alone
- Uncertainty about full-shift personal exposure
- Different work patterns between employees in the same role
- Work spread across day, evening, night or weekend shifts
When dosimetry may not be needed
When dosimetry may not be necessary
Fixed or task-based sound measurements can sometimes characterise exposure more efficiently than dosimetry. The monitoring strategy should match the workplace and the assessment objective rather than defaulting to one method.
- Tasks are simple and consistent across the shift
- Exposure duration is well known and documented
- Workers remain in a defined, fixed location
- Measured sound levels are stable over time
- Representative measurements can be obtained reliably from fixed positions
A broader workplace noise survey will identify whether dosimetry, fixed measurements or a combination is the right approach for your operations.
How it works
How a personal noise dosimeter works
Microphone placement
The microphone is positioned in the hearing zone — typically on the shoulder — so the measurement reflects what reaches the worker's ear.
Instrument configuration
Dosimeters are configured for the relevant exchange rate, criterion level and integration parameters before the shift begins.
Measurement period
The instrument records continuously across the agreed monitoring period — full shift or task-based — without interruption where possible.
Cumulative exposure recording
Sound energy is integrated over time so the total dose and equivalent continuous level can be calculated.
Time-history data
Where available, second-by-second time-history allows individual events and tasks to be related back to specific activities.
Calibration checks
Pre- and post-use field calibration with an acoustic calibrator confirms the instrument was within tolerance throughout monitoring.
Activity recording
Observation logs document the tasks, locations, breaks and unusual events that put the dosimetry data into context.
Dose and exposure metrics
Results are expressed as LEX,8h, dose or projected dose, and where appropriate LCpeak — interpreted against UK action and limit values.
The process
The dosimetry process
Each dosimetry programme is scoped to the workplace. The workflow below is typical; not every step applies to every project, and not every employee needs to be monitored.
- 1
Initial consultation
Understand the workplace, work patterns and the questions the dosimetry programme is intended to answer.
- 2
Review jobs, shifts and work patterns
Map out roles, shift structures and movement between work areas before designing the monitoring plan.
- 3
Identify representative employees
Select workers whose shift will represent each similar exposure group, rather than monitoring every individual.
- 4
Select suitable monitoring periods
Agree which shifts, days and tasks the dosimetry should cover so the result reflects normal operations.
- 5
Explain monitoring to participating workers
Brief each participating employee on how the dosimeter is worn, what it records and how to handle it during their shift.
- 6
Correct dosimeter fitting
Fit the instrument so the microphone sits in the hearing zone, secured against movement and clear of obstruction.
- 7
Pre-measurement calibration
Field-calibrate the dosimeter with an acoustic calibrator immediately before the monitoring period begins.
- 8
Observation and activity logging
Record tasks, locations, breaks and unusual events alongside the measurement so peaks and changes can be linked to real activities.
- 9
Monitoring during representative work
Allow the worker to follow their normal routine through the agreed monitoring period without altered behaviour where possible.
- 10
Review of unusual events
Note any breakdowns, atypical tasks or interruptions so they are not mistaken for normal exposure during interpretation.
- 11
Post-measurement calibration
Re-check calibration after the shift to confirm the instrument remained within tolerance throughout monitoring.
- 12
Data download and validation
Transfer measurement files and time-history data, then validate against observation records before any calculations.
- 13
Exposure interpretation
Calculate LEX,8h and related metrics, identify contributing tasks and compare against the relevant action and limit values.
- 14
Reporting and recommendations
Issue a clear written report covering methodology, results, interpretation and prioritised, practical next steps.
Representative workers
Selecting representative workers
Dosimetry is normally carried out on representative members of a similar exposure group rather than every employee. The selection and the rationale behind it are documented so the assessment is transparent.
Similar exposure groups
Workers with comparable tasks, locations and patterns are grouped so a representative sample characterises the group.
Representative employee selection
Selected workers reflect typical work — not the quietest day, the busiest day or an atypical role.
Variation between workers
Where members of a group differ materially in exposure, the grouping is revisited and additional monitoring carried out.
Different shifts and conditions
Day, evening, night or weekend shifts may need separate monitoring where production patterns differ.
Mobile and non-routine activities
Mobile and variable roles often need more than one monitored shift to fairly represent normal work.
When to monitor more than one worker
Where one shift cannot represent the group, additional employees are monitored before drawing wider conclusions.
One worker's result does not automatically represent an entire workforce. Where activities or conditions differ materially between employees, additional monitoring is carried out.
Activity logs
Activity logs and worker observations
Dosimeter data is most useful when it can be tied back to what was actually happening during the shift. Observation alongside measurement allows peaks and changes to be connected to real workplace activities.
- Task start and finish times
- Machinery and tools used during each task
- Locations and work areas visited
- Breaks and time away from the work area
- Unusual events, breakdowns or atypical conditions
- Temporary noisy activities not part of routine work
- Use of hearing protection during the shift
- Worker comments about the day's work
- Observer notes on production conditions and pace
Understanding results
Understanding dosimetry results
Personal noise dosimetry typically reports daily personal exposure (LEX,8h), measured dose or projected dose for the monitored period, the exposure duration covered, and any significant high-noise periods identified during the shift. Where time-history data is available, the contribution of different tasks can be quantified.
Peak sound pressure (LCpeak) may also be reported where the instrument and assessment method support it, particularly in workplaces with impact, impulsive or pneumatic noise sources. Results are compared against the lower and upper exposure action values and the exposure limit value defined in the Control of Noise at Work Regulations 2005.
A single percentage on the dosimeter screen is not a compliance verdict. Professional interpretation considers measurement quality, representativeness, observed activity and the wider control programme before any conclusion is drawn.
Daily exposure
Daily exposure and LEX,8h
LEX,8h is the daily personal noise exposure level, expressed in dB(A) and normalised to a notional eight-hour working day. Varying noise levels across a shift are combined by their energy and duration so a single comparable figure can be reported for each monitored worker.
Where the monitored period is shorter or longer than a standard eight-hour shift, results are normalised to the eight-hour reference period. Shorter or longer monitoring periods may need additional professional interpretation, and the monitored period must still be representative of the worker's typical exposure pattern.
Because LEX,8h depends on both level and duration, dosimetry results cannot be interpreted from sound level alone. Further background on the calculation and its regulatory context is covered on our noise exposure assessment page.
Monitoring strategy
Full-shift versus task-based dosimetry
The two approaches answer different questions. The correct strategy may combine dosimetry with calibrated sound-level measurements at specific tasks.
Full-shift monitoring
Across the whole working day
- Useful where exposure varies throughout the day
- Captures task changes and movement between areas
- Requires accurate activity information alongside the data
- May include non-representative events that need professional review
Task-based dosimetry
Focused on defined activities
- Useful for defined, repeatable activities
- Helps isolate the exposure contribution of specific tasks
- Can support exposure modelling combined with task durations
- May not represent the entire shift by itself
Quality control
Dosimeter placement and worker behaviour
Measurement quality depends on how the instrument is fitted, how the worker is briefed and how the shift is observed. These are practical measurement controls — not criticisms of the workers taking part.
- Microphone positioned near the ear or hearing zone
- Microphone clear of obstruction by clothing, PPE or hair
- Instrument securely fitted and unlikely to shift during work
- Workers following normal routines wherever possible
- Any removal or interruption documented at the time
- Care to avoid radios, compressed-air misuse or direct microphone contact
- Suspicious or non-representative peaks reviewed against activity logs
Data quality
Sources of unreliable dosimetry data
A competent dosimetry programme identifies and manages questionable data rather than accepting it at face value.
- Incorrect microphone position away from the hearing zone
- Microphone rubbing against clothing or PPE
- Instrument removal during the monitored period
- Direct impacts on the microphone
- Abnormal production conditions during monitoring
- Unrecorded changes in work activity or location
- Monitoring an unusually quiet or unusually busy period
- Incomplete or inaccurate activity records
- A monitoring duration that does not reflect normal work
- Incorrect instrument configuration
- Failed pre- or post-use calibration checks
Hearing protection
Dosimetry and hearing protection
Personal noise dosimeters normally measure external sound exposure at the microphone position. The recorded level should not be treated automatically as the sound actually reaching the ear beneath hearing protection.
Hearing protection performance depends on the device selected, how well it fits, its condition and whether it is worn consistently throughout exposure. Dosimetry findings help determine where formal hearing protection assessment may be required, and inform the selection of suitable PPE — but hearing protection should not automatically replace engineering and organisational controls.
Where formal review is needed, our hearing protection assessment service covers attenuation suitability, PPE compatibility, fitting and consistent use as part of the wider Workplace Noise Surveys programme.
Industries & roles
Industries and worker roles
Personal noise dosimetry across UK industrial and commercial workplaces, with worker roles typically including:
Production operators
Maintenance engineers
Fabricators
Welders
Woodworking operatives
Warehouse staff
Logistics workers
Construction workers
Recycling operatives
Mobile technicians
Plant-room engineers
Multi-skilled employees
Supervisors across work areas
Deliverables
What the client receives
- Agreed monitoring strategy and shift coverage
- Representative worker selection with rationale
- Personal dosimetry results for each monitored employee
- Activity and task records aligned to the measurement period
- Daily personal exposure interpretation
- LEX,8h findings normalised to an eight-hour working day
- Identification of significant exposure periods during the shift
- Peak sound pressure findings where appropriate
- Comparison with the relevant action and limit values
- Identification of high-contribution tasks and activities
- Recommendations for any additional measurements required
- Prioritised, practical control recommendations
- Hearing protection observations and selection considerations
- Clear technical report with practical next steps
Personal noise dosimetry provides competent measurement, interpretation and recommendations to support employer duties under the Control of Noise at Work Regulations 2005. It does not constitute legal certification or a guarantee of compliance.
From findings to controls
How dosimetry supports noise control
Dosimetry helps target where engineering, organisational and hearing protection controls will have the greatest effect — and to confirm whether those controls remain effective over time.
Identify high-contribution tasks
Pinpoint the activities driving daily exposure so controls target the right work.
Prioritise engineering controls
Direct damping, enclosure or substitution measures at the tasks where they will have most effect.
Review work scheduling
Reorganise rotations and timing so loud work occupies a smaller share of any one worker's shift.
Reduce unnecessary exposure duration
Eliminate avoidable time spent in high-noise areas without compromising the work.
Assess process changes
Use dosimetry to evaluate whether process or equipment changes have altered exposure as expected.
Confirm controls remain effective
Repeat monitoring after engineering or organisational changes to verify the intended reduction.
Target further task measurements
Use dosimetry findings to scope follow-up sound-level measurements at the noisiest activities.
Inform hearing protection decisions
Combine exposure findings with hearing protection assessment to select and apply suitable PPE.
Support workplace noise risk assessment
Feed dosimetry results into the broader workplace noise risk assessment as measurement evidence.
Why us
Why choose Workplace Noise Surveys
Occupational hygiene-led monitoring
Dosimetry designed around employee exposure and risk control, not just an instrument reading.
Representative worker selection
Sampling planned around similar exposure groups and normal operating conditions.
Properly configured equipment
Dosimeters configured for the relevant exchange rate, criterion level and integration parameters before each programme.
Calibration and quality checks
Pre- and post-use field calibration with acoustic calibrators and review of any non-representative data.
Workplace observation
Activity logs and on-site observation alongside the measurement so peaks and changes have context.
Defensible interpretation
Results compared against UK action and limit values, with clear recognition of measurement uncertainty.
Clear reporting
Written reports suitable for internal compliance records, with prioritised practical next steps.
Green Air Monitoring network
Supported by the wider Green Air Monitoring occupational hygiene network across related workplace exposure disciplines.
For broader compliance assessment see our workplace noise surveys service, the wider workplace noise monitoring programme that produces measurement evidence, or noise exposure assessment for interpretation of overall employee exposure. Learn more about us or get in touch.
FAQ
Personal noise dosimetry FAQs
What is a personal noise dosimeter?+
A personal noise dosimeter is a small, body-worn instrument that records a worker's noise exposure over time. The microphone is positioned close to the hearing zone — typically on the shoulder — so that the cumulative sound the employee experiences during their work activities can be measured and later analysed against the Control of Noise at Work Regulations 2005 framework.
When is personal noise dosimetry required?+
Personal dosimetry is most appropriate where exposure varies by task, location, shift or work pattern — for example mobile maintenance work, multi-area duties, intermittent high-noise activities or roles where fixed measurements cannot reasonably represent personal exposure. It is one of several measurement methods; the right approach depends on the work being assessed.
Does every employee need to wear a dosimeter?+
No. Dosimetry is normally carried out on representative workers within each similar exposure group rather than on every individual. The selection of representative employees, and the number monitored, is based on how variable the work is and how reliably the group's exposure can be characterised from sampled shifts.
How long should a noise dosimeter be worn?+
The monitoring period must be long enough to represent the worker's normal exposure pattern. This is often a full shift, but task-based dosimetry may use shorter, focused periods covering specific activities. Whatever the duration, it must be representative of the work; an unusually quiet or atypical period will not produce a meaningful result.
Can a dosimeter measure a full work shift?+
Yes. Modern personal noise dosimeters are designed for shift-length monitoring and record cumulative exposure, time-history data and significant events across the period worn. Full-shift dosimetry is particularly useful where workers move between tasks and areas, provided activities are observed and documented alongside the measurement.
What does LEX,8h mean?+
LEX,8h is daily personal noise exposure, expressed in dB(A) and normalised to a notional eight-hour working day. It combines the contribution of each task an employee performs over their shift so different workers and shift lengths can be compared on a common basis, and so exposure can be interpreted against the action and limit values.
Can personal dosimetry identify the noisiest tasks?+
Where dosimetry is supported by a detailed activity log and, ideally, time-history data, the contribution of individual tasks to overall exposure can usually be identified. This makes dosimetry a useful tool for prioritising engineering controls, work-pattern changes and further task-based measurements.
Does a dosimeter measure the noise beneath hearing protection?+
No. A personal noise dosimeter normally measures sound at the microphone position outside any hearing protection. The result should not be treated as the level reaching the ear underneath ear defenders or plugs — that depends on the selection, fit, condition and consistent use of the hearing protection, and is evaluated separately as part of hearing protection assessment.
Can one worker's result represent other employees?+
Sometimes, but not automatically. Where workers share a similar exposure group — comparable tasks, locations and work patterns — a representative result can characterise the group. Where activities, shifts or production conditions differ materially between employees, additional workers should be monitored before drawing wider conclusions.
What can make dosimeter results unreliable?+
Common causes include incorrect microphone position, clothing or PPE rubbing the microphone, the instrument being removed during the shift, direct impacts on the microphone, unusual production conditions, incomplete activity records, monitoring an atypical period or failed pre/post calibration checks. Professional review identifies and manages questionable data rather than accepting it at face value.
Is personal noise dosimetry the same as a workplace noise survey?+
No. A workplace noise survey is the broader assessment exercise, which may include area measurements, task measurements, dosimetry, observation, interpretation and reporting. Personal noise dosimetry is one measurement method within that wider survey — focused specifically on an individual worker's changing exposure during representative work activities.
Arrange Personal Noise Dosimetry
Speak to a UK occupational noise specialist to scope a dosimetry programme, agree representative workers and arrange monitoring dates. We respond to most enquiries the same working day.