What Is Personal Noise Dosimetry?

Personal noise dosimetry is a structured method of measuring occupational noise exposure at the individual worker. A small body-worn instrument — the dosimeter — records sound near the hearing zone over time, as the wearer carries out normal tasks. The result is a record of exposure that follows the person, rather than a single fixed measurement at one position.

Unlike a handheld sound-level measurement, which describes the level at a chosen point at a chosen moment, dosimetry captures the way exposure changes through a representative shift. That makes it especially valuable where work patterns vary, where workers move between areas, or where tasks combine in ways that cannot be reconstructed from spot readings alone.

Dosimetry supports occupational noise exposure assessment by providing time-resolved data that can be interpreted against the UK exposure action and limit values. The data on its own is not the assessment; it must be reviewed alongside activity records and an understanding of the work performed.

Depending on configuration, a personal noise dosimeter can record sound level over time, equivalent continuous sound level (LAeq), cumulative noise dose, projected dose and LEX,8h or equivalent exposure metrics. Many instruments also record maximum levels and C-weighted peak sound pressure (LCpeak) where supported.

The available outputs depend on the instrument and on the settings used at configuration. Reported values should always be considered alongside the criterion level, exchange rate and threshold that were applied.

LEX,8h is the daily personal noise exposure level expressed in dB(A), normalised to a notional eight-hour working day. It combines the equivalent continuous sound level of each activity with the duration of that activity, producing a single figure that can be compared with the UK exposure action and limit values.

LEX,8h is not the same as the live reading shown on a sound-level meter. It is a calculated quantity that depends on the representativeness of the monitoring period. Short sampling, unrepresentative shifts and incomplete activity records all affect how reliably it can be reported. For the corresponding action values, see understanding noise action values.

Dosimetry results may support comparison with the lower, upper and limit exposure values once they have been interpreted into daily or weekly personal exposure. Peak sound pressure is considered separately from daily average exposure, regardless of how the average is derived.

Comparison with action values should be carried out by a competent person who has reviewed the activity log, the time-history and any non-representative events. For the structure of the action values themselves, see understanding noise action values.

No. Workers are normally grouped into similar exposure groups based on the tasks, locations and shift patterns they share, and representative individuals are selected from each group. One result does not automatically represent everyone, and the size of the sample should reflect variability between workers and between shifts.

Where work patterns differ materially within a group, or uncertainty is high, additional dosimetry across more workers or more shifts may be needed before exposure is generalised to the wider workforce.

Day, evening and night shifts can present materially different exposure. Production rates may vary, staffing may be different, maintenance and cleaning often happen at specific times, and start-up and shutdown can introduce short high-level activities. Monitoring a single shift may not represent the full range of exposure across the operation.

Where shift variation is significant, dosimetry can be repeated across the relevant shifts, with results combined and interpreted together. The assessment scope should make clear which shifts the conclusions apply to.

Data is downloaded and validated, activity logs reviewed and exposure calculated. High-contribution tasks are identified, peak findings are reviewed independently of average exposure, and results are compared against UK action and limit values. Control recommendations, hearing-protection review and reporting follow.

Where data quality is insufficient — for example because of interference, calibration failure or unrepresentative work — monitoring may need to be repeated before findings are relied upon.