3M Noise Measurement

Measure noise with a hearing conservative programme

Noise measurement is a fundamental part of the Hearing Conservation Programme (HCP). Noise survey results are the basis for decision-making on reducing risk and taking protective action.

Do we need a Hearing Conservation Programme (HCP)?

  • 3M Detection Solutions

    If employees at your company work in noisy areas, start by conducting a sound (or noise) survey. 

    The European Physical Agents (Noise) Directive 2003/10/EC outlines the duty of employers to protect their employees from risk of exposure to noise. There are three different exposure action values defined in the Directive.

    Lower Exposure Action Value (LEAV) LEX,8h = 80dB(A) and 135dB(C) Peak
    Upper Exposure Action Value (UEAV)LEX,8h = 85dB(A) and 137dB(C) Peak
    Limit Value (LV) LEX,8h = 87dB(A) and 140dB(C) Peak

    Depending on the level of risk involved, employers are required to take action to reduce the risk of noise exposure. Hearing protection must be made available to employees at LEAV, and strictly enforced at UEAV.

    The role of hearing protectors is clearly defined in the context of achieving the Limit Value.

    Noise surveys can be simple or complex, and must be conducted by a competent person, such as your health and safety team or by a consultant. There are many different types of noise measurement instruments available depending on the type of noise and the purpose of the survey.

    Measure noise to answer key questions

    • Is HCP needed?
    • Can we control the noise?
    • How much hearing protection do we need?

    Some indications that noise may be a problem in your workplace

    • Employees hear ringing or humming in their ears after exposure to loud sounds
    • The noise is so loud that employees need to shout to be heard by a colleague approximately 2 metres away
    • Employees notice temporary loss of hearing ability when leaving work

Key Takeaways

    • A Hearing Conservation Programme is typically triggered on reaching the Upper Exposure Action Value, or in some cases at LEAV. Check your national regulation for more information.
    • Area monitoring is a useful starting point.
    • Personal monitoring (noise exposure of an individual worker) is needed when workers are highly mobile and noise levels vary considerably.
    • Detailed noise measurements with an octave band analysis may be needed for developing noise control solutions.
  • • Action level (AL)

    • Dose

    • Dosimeter

    • Exchange rate

    • Octave Band Analysis

    • Exposure Action Values and    Limit Values

    • Sound (Noise) Surveys

    • Sound level meter (SLM)
    • Time weighted average (TWA)
    • Weighting

Getting Started with Sound Surveys

  • 3M Detection Solutions

    Step 1. Perform a walkaround survey
    A walkaround survey or 'screening' survey can be the first step towards identifying high-risk noise areas. Their purpose is to identify where hazardous noises are present. If measured noise levels are 80 dB(A) or more, further measurements may be required to assess the risk of exposure.

    Step 2. Conduct sound level surveys in noisy areas
    A sound level survey is a systematic method for measuring sound pressure levels of specific equipment or tasks, in an area, or near a person. Types of Sound Level Surveys include:

    • Basic survey: Helps an employer to quantify the noise environment, create noise maps of area sound levels, and determine if a more extensive survey is needed. The results can be used to create a sampling plan; an estimate of how many samples need to be taken to accurately assess the noise levels for each area or job description.
    • Extensive survey: Involves gathering detailed information about specific job tasks, areas, or equipment. Results are useful in determining worker noise exposures, make hearing protection assignments, and identifying who is in or out of the HCP.
    • Noise control survey: Focuses on identifying and prioritising options for reducing noise hazards using engineering or administrative controls.

    Step 3. Create a noise sampling plan
    The results of your basic sound level survey and your observations of how noise fluctuates during the work day can help you develop a plan for how many measurements need to be taken in order to accurately assess the noise exposures in each area and for each task or job description. Generally, more samples are needed when the results of your basic survey are close to the permitted exposure level for noise and when the variability of your noise survey results is high. Fewer samples may be needed if the sound levels in your surveys are well below the permitted level and the sound levels are less variable.
    Refer to your national regulation for guidelines on risk assessment and sampling requirements.

    Step 4. Monitor employee noise exposures
    Measuring the noise exposure of employees requires averaging the sound levels over time. Noise exposure monitoring is often included as part of an extensive sound survey. The purpose of noise exposure monitoring is to determine a worker’s 8-hour time weighted average LEX,8h exposure or accumulated noise dose over the work shift (personal noise dose). It is also used to measure how noise varies over time according to the job task.

Getting Started with Sound Measurement Instrumentation

Learn More About Noise Exposure Instrumentation

Sound measurement instrumentation should be rugged and reliable and include a software system that detects, measures, evaluates, and reports any occupational and environmental safety hazards.

Sound level meters (SLMs) measure sound pressure levels in real time. At least a general purpose meter (Type 2 microphone) and specific instrument settings are needed for occupational sound surveys. SLMs can be basic or have advanced features and capabilities. 

  • Measure and display the sound level in real time. They do not average or store results.

  • In addition to measuring and displaying sound levels, advanced SLMs can average, or integrate sound levels over time. This is an important function, because risk of hearing loss and noise exposure limits are based on the average sound levels measured. These devices may also have special filters to measure impulse/impact noise or octave band filters to divide the sound spectrum into smaller segments.

  • Personal noise dosimeters are portable devices worn by workers for extended periods of time throughout the work shift. At the end of the sampling period, this instrument automatically calculates the time-weighted average, noise dose, and other important metrics. It is common practice for employers to use representative personal sampling when workers move locations frequently and/or when noise levels are variable.

  • All sound measurement instruments need to be routinely calibrated. It is recommended that instruments be calibrated annually by the manufacturer or an accredited third-party to ensure the accuracy of the measurement device. Each time a sound measurement instrument is used, it should be checked with an acoustical calibrator, designed for that instrument. The sound level reading should be the same at the beginning and end of each measurement period.

  • Noise measurement instruments are categorized by Type or Class according to the accuracy of the microphones. Type 2 (class 2) general purpose instruments are designed to be accurate to +/- 2 dB . For most hearing conservation program noise measurements, a Type 2 instrument is considered adequate. A more accurate Type 1 instrument may be used by engineers to conduct detailed noise control surveys but is generally not needed for basic sound level surveys.

  • There are many apps for mobile phones and tablets that can be used to measure sound. These apps may be useful for teaching employees about sound levels in your facility and demonstrating how sound levels vary by area and task. However, mobile phones and tablets should not be used for conducting noise surveys as part of an occupational HCP unless a Type 2 microphone is used and the calibration of the device is checked before and after each measurement.

Sound Measurement Instrument Settings

  • 3M Sound Measurement

    The results of a sound level survey depend on the measurement settings used. Check your local regulations for any specific requirements.
    For the purpose of selecting appropriate hearing protectors, sound level measurements using A-weighted and C-weighted filters incorporated in your measuring device are often sufficient. These measurements can provide valuable information on the noise characteristics. Consider the following examples.

    Example 1: When the difference between the C-weighted and A-weighted sound is less than 2 (LC – LA ≤ 2), the sound is dominated by high/medium frequencies.

    Example 2: When the difference between the C-weighted and A-weighted sound is greater than 2 (LC – LA ≤ 2), the sound is dominated by medium/low frequencies. The higher the difference, the greater the low frequency content.

    This information can be very useful when selecting hearing protectors for different applications.

    For hearing conservation, a filter setting on sound measurement instruments, known as A-weighting, is used. When this is done, the sounds that are included in the measurement are limited to a range of sound frequencies where human ears are most sensitive and the risk of hearing damage from noise is greatest.

    The C-weighted filter corresponds best to the subjective reception of sounds at high sound pressure levels and is normally used for measuring sounds dominated by low frequencies. This filter is also used for measuring peak impulse sound when set on fast response.

    Slow response
    The decibel reading displayed on a sound level meter is an average of the sound level measured over a certain time. For hearing conservation, a slow response setting is used, meaning that the value on the display is the 1-second average that was measured while the instrument is on.

What is Required?

The European Council Directive 2003/10/EC does not provide specific guidelines on how frequent noise measurements should be repeated. Typically, risk assessment (which may include noise measurement) are repeated whenever there is a change in processes, procedures, or exposure time that may lead to changes in employee noise exposures. Many companies choose to conduct surveys periodically (once every year or two) to ensure that all exposed employees are included in their hearing conservation programmes.

  • Occupational Noise Exposure
    Key requirements of the European Council Directive 2003/10/EC
    • Employer must assess and, if necessary, measure the levels of noise to which workers are exposed
    • Noise measurement sampling must be representative of the personal exposure of the worker
    • Risk assessment and noise measurement must be carried out by a competent person/service provider at suitable intervals
  • Permissable Exposure Limit
    • When carrying out risk assessment, particular attention should be given to the following:
      • • Level, type and duration of noise exposure – including impulse noise
      • • Exposure limit values and exposure action values
      • • Any effects concerning the health and safety of workers belonging to particularly sensitive risk groups
      • • Information on noise emission and control measures
      • • Availability of suitable hearing protectors with adequate attenuation
      • • Responsibility for enforcement of the use of hearing protectors in designated areas lie firmly with the employer
    • Health surveillance, including audiometric checks, must be carried out when the worker’s noise exposure exceeds the upper exposure action value and offered as a preventative measure to workers whose exposure exceeds the lower exposure action value

Beyond the Basics

Download Noise Exposure Infographic*** (PDF, 167.21 KB)

Employers may choose proactive policies to better protect exposed workers. Best practices for noise measurement include:

  • 3M Occupational Noise Limits Infographic

    Lower the Limits
    Some employers have opted to implement exposure limits below the Lower Exposure Action Value as an additional safeguard to better protect workers from developing NIHL.

    Plan Ahead
    Keep noise measurement data up-to-date by repeating surveys every one to two years or sooner, if and when any changes in equipment or personnel occur. Repeat noise surveys after implementing engineering controls. Calibrate noise survey equipment annually. Conduct calibration checks before and after each measurement to verify the reliability of the instruments.

    Be Thorough
    Conduct enough samples to ensure that noise measurements are representative of the worker’s exposures. This may require a statistical sampling approach. Document areas and jobs that have noise levels and/or exposures that are less than LEX,8h 80 dB(A) as well as those at or above LEX,8h 85 dB(A).

    Use Your Results
    Create a database of noise survey records that can be easily accessed and maintained over time. Review noise survey results routinely: identify changes in noise levels or job tasks that trigger the need for additional monitoring.

    Get Help
    Consider contracting with a noise specialist for guidance and detailed survey requests that go beyond the expertise of the employer. Engage workers in identifying noise problems and solutions.

    *Noise Exposure Infographic Copyright 3M 2017. All rights reserved

Have You Considered?

  • Noise Exposure Variance
    How much do noise exposures vary?
    • Does each job classification have an assigned daily time weighted average noise exposure level?
    • Have you measured all occasional or seasonal noisy activities?
    • Have changes in the length of work shifts been accounted for?
    • Is it clear which jobs are NOT required to be in the hearing conservation programme (HCP)?
  • Noise Exposure Reduction
    Can it be better?
    • Can lower noise limits be adopted as company policy?
    • Can you use the noise survey results to identify projects for noise control?
    • Is noise interfering with workers’ ability to communicate?
  • Noise Exposure Protection
    Who knows the noise?
    • Do workers know their noise exposures and how to protect themselves?
    • Are the noise survey results part of the hearing test records?
    • Are signs posted to alert workers of high noise areas and provision of suitable hearing protects?
    • Do workers know how and when to wear their hearing protectors as part of control measures?


This information is based on selected current national requirements. Other country or local requirements may differ. Always consult user instructions and follow national regulations. This website contains an overview of general information and should not be relied upon to make specific decisions. Reading this information does not certify proficiency in safety and health. Information is current as of the date of publication, and requirements can change in the future. This information should not be relied upon in isolation, as the content is often accompanied by additional and/or clarifying information. All applicable national laws and regulations must be followed.

Contact your local 3M office for further information.