How Is Workplace Noise Measured?

When is noise measurement needed?

Art. 6 of the Regulation on the Protection of Workers from Noise-Related Risks requires the employer first to address the noise level in the risk assessment and, where the results of the risk assessment make it necessary, to determine exposure by having a noise measurement carried out. The same article sets three requirements for the measurement method: the method and instruments must be suited to the nature of the noise, the duration of exposure and the ambient conditions; they must allow a decision on whether action and limit values are exceeded; and they must show the worker's personal exposure. The results are kept to be shown in a labour inspection.

In practice, the following signs indicate the need for measurement:

• You have to raise your voice to talk to someone one metre away.
• There are known noise sources such as presses, grinding, compressors, looms, crushers or impact hand tools.
• A new machine has arrived, the line layout has changed or the shift pattern has lengthened.
• Audiometry results show the onset of hearing loss, or workers complain of ringing in the ears.

We explained what is required of the employer at 80, 85 and 87 dB(A) in our article on exposure values in the noise regulation. This article focuses on how the figure to be compared with those values is obtained.

The difference between area measurement and personal dosimetry

The Ministry's noise guide prepared for the foundry sector classifies measuring instruments as instantaneous noise meters, sound level meters and personal dosimeters. In the workplace, two approaches complement each other:

The microphone of a personal noise dosimeter is attached to the worker's shoulder, at a point close to the ear, and the measurement continues for the full shift where possible. The TS EN ISO 9612 standard used to determine occupational noise exposure defines three strategies for the measurement plan: task-based, job-based and full-day. Always check in the report which standard and which strategy the laboratory used; the strategy directly affects the measurement time and how many workers are measured.

Area noise measurement, on the other hand, is needed to find sources and see the effect of measures. An area measurement repeated at the same point after an enclosure or silencer has been fitted shows whether the investment has worked.

How is daily exposure (LEX,8h) calculated?

Art. 4 of the Regulation defines the daily noise exposure level (LEX,8h) as the time-weighted average for an eight-hour working day of all A-weighted noise exposures. For a worker exposed to different levels during the day, the calculation is as follows:

LEX,8h = 10 × log₁₀ [ (1/8) × Σ (Tᵢ × 10^(0.1 × LAeq,ᵢ)) ]

Here Tᵢ is the duration of each task in hours and LAeq,ᵢ is the equivalent sound level during that task.

Example: In a metal parts workshop in Bursa, a press operator is exposed to 92 dB(A) for 4 hours a day at the press, 85 dB(A) for 2 hours next to the grinding section and 75 dB(A) for 2 hours in the break and preparation area. The calculation gives LEX,8h ≈ 89.4 dB(A). This value is above the upper action value of 85 dB(A); hearing protection is mandatory, an action plan containing technical and organisational measures is prepared and the area is marked. Whether the 87 dB(A) limit value is complied with is assessed taking into account the protective effect of the hearing protection (Art. 5/2).

In the same example, if the time at the press is reduced to 2 hours and the operator spends those 2 hours in the 85 dB(A) area, the result is about 87.5 dB(A). In other words, halving the time on the noisiest task gains about 2 dB; what really reduces exposure is improving the press itself. One rule is useful in the calculation: doubling the time at the same level increases the result by about 3 dB.

In work with impulse noise (hammering, riveting, die impacts), the peak sound pressure (Ppeak) is also measured and compared with 135, 137 and 140 dB(C). For work where daily exposure varies markedly from day to day, the Regulation allows the weekly exposure level to be used; however, the weekly level may not exceed 87 dB(A) either (Art. 5/4).

How is a noise map prepared?

A noise map is created by plotting area measurement results on the plan of the production area. It is prepared as follows:

1. The current layout plan of the hall is obtained and a measurement grid suited to the size of the facility is drawn.
2. Measurements are taken at each point of the grid at the normal production pace, with the machines running.
3. The results are divided into colour bands: below 80 dB(A), 80–85 dB(A) and above 85 dB(A).
4. Sources, workstations and walkways are marked on the map.

The map serves three purposes. The first is the provision in Art. 8/3 of the Regulation: places where the upper action value is exceeded are marked, their boundaries are set and, where technically possible, access is controlled. Second, it shows whether the noise in rest areas is suitable for their purpose (Art. 8/4). Third, it lets you choose the quietest area when deciding where to put a new machine. Do not use the map in place of personal exposure; it shows which area is risky, not who is exposed and how much.

Planning the measurement step by step

Noise measurement cannot be carried out by just any firm the employer appoints. Under the Regulation on Laboratories Performing Occupational Hygiene Measurements, Tests and Analyses, published in Official Gazette No. 28741 of 20 August 2013, the laboratory carrying out the measurement must hold a competence or preliminary competence certificate from the İSGGM; the result of an uncertified laboratory is invalid. The laboratory notifies the measurement to ISG-KATİP (the Ministry's online OHS registration system) at least 3 days in advance. We plan the measurement with authorised laboratories and health institutions and enter the results in the risk assessment. The planning sequence is as follows:

1. List the noisy jobs. Extract the noise sources, and the tasks carried out near them, from the risk assessment.
2. Form similar exposure groups. Workers doing the same job under the same conditions form a group; the laboratory selects representatives from each group.
3. Choose a representative day. A day when capacity is reduced, maintenance is being carried out or half the machines are stopped gives a misleading result.
4. Inform the workers. A worker wearing a dosimeter must not cover the microphone or remove the device; changes of task during the day are recorded.
5. Enter the result in the risk assessment. LEX,8h values, the action plan, the PPE decision and the audiometry plan should come together in the same document.
6. Plan the repeat. The legislation does not set a fixed repeat interval for noise measurement; the measurement is renewed when there is a new machine, a change of layout or shift, and at the interval set by the risk assessment.

What should you check in the noise measurement report?

The noise measurement report you receive should contain the following information:

• The laboratory's competence certificate, and confirmation that the certificate covers the noise parameter.
• The date of measurement, the shift and the machines running that day.
• The tasks of the workers measured, the measurement times and the strategy used.
• Calibration details of the instruments and the measurement uncertainty.
• LEX,8h and, where necessary, Ppeak values for each group, with a comparison against 80, 85 and 87 dB(A).
• Assessment and recommendations: which measure has priority at which source.

Typical report problems that make the result unusable are: the whole hall being represented by an area measurement taken at a single point, the ratio of measurement time to the shift not being stated, break and meal times not being deducted from the calculation, and the noisiest machine being under maintenance on the day of measurement. If any of these applies, ask the laboratory for an explanation before entering the result in the risk assessment.

The results also determine health surveillance: if the 85 dB(A) upper action value is exceeded, hearing tests are mandatory, and they can also be carried out above 80 dB(A). For test frequency, see our article on periodic examinations and tests, and for selecting hearing protection, our article on PPE selection. The 2026 base administrative fine for failing to have the necessary measurements carried out is TL 33,326, and the amount is increased according to the hazard class and the number of workers; for the calculation, you can use the administrative fines tool.

Metal and machinery manufacturing is the sector where noise measurement comes up most often; for sector-specific risks, see our metal and machinery page, and for entering measurement results in the document, our risk assessment service.

Frequently Asked Questions

How often is noise measured?

The Noise Regulation does not set a fixed interval. Measurement is carried out when the risk assessment considers it necessary, and is renewed with every change that affects exposure, such as a new machine, a change of layout or longer working hours.

Should I have personal dosimetry or area measurement carried out?

The Regulation requires the measurement to show the worker's personal exposure. For workers who move around during the day, a dosimeter shows this best; at fixed stations, task-based measurement may be sufficient. Area measurement is also needed to find sources and for the noise map.

Can an OSGB carry out noise measurement?

Only a laboratory holding a competence or preliminary competence certificate from the İSGGM can carry out the measurement. The OSGB's (joint health and safety unit's) role is to identify the need for measurement, plan it with the laboratory and reflect the results in the risk assessment and health surveillance.

What is done if the measurement result is above 85 dB(A)?

Wearing hearing protection becomes mandatory and is checked, an action plan containing technical and organisational measures is implemented, the area is marked and hearing tests are carried out on workers. After the measures, the measurement is repeated to confirm their effect.