Noise measurement forms the foundation for the entire HCP. Results from a Noise Assessment will help identify work locations where noise is a problem, where additional noise measurements need to be made, which workers are at risk of hearing loss, determine what noise sources and processes are causing that risk, identify the kind of noise control measures that could be implemented, and check the effectiveness of existing control measures already in place.
The Safe Work Australia (SWA), Code of Practice (COP): Managing hazardous noise and preventing hearing loss at work’ 2018, advises that unless hazardous noise identified in the workplace can be reduced to exposures below the standard immediately, a noise assessment should be conducted.
Work Health and Safety Legislation in Australia state the Workplace Exposure Standard (WES) for noise, in relation to a person, is:
There are two parts to the exposure standard for noise because hazardous noise can cause two types of hearing loss. Gradual hearing loss, called noise induced hearing loss (NILH), happens over a period of time and is caused by noise that exceeds 85dB(A). Immediate hearing loss, called acoustic trauma, can be caused by noise generated by a single intense impulse noise or brief exposure to noise that exceeds 140 dB(C).
The SWA COP also recommends that until revised standards are established for ototoxic substances, the daily noise exposure of workers exposed to ototoxic substance, should be reduced to:
More information on ototoxins can be found in AS/NZS 1269.0 (Appendix C) and a list of the most commonly used Ototoxic Substances in the Workplace are listed in the SWA COP (2018) (Appendix B).
LAeq,8h of 85 dB(A) means that an unprotected worker cannot be exposed to more than 85 decibels continuously over an eight-hour shift. The permitted time of exposure for an unprotected worker decreases as the noise exposure level increases. For example, an exposure at 88 dB(A) for 4 hours, is equivalent to 8 hours of continuous exposure at 85 dB(A). This is because the decibel (dB) scale is logarithmic, and decibels aren't linear like normal numbers. A 3 dB increase on this scale equals a doubling of the sound energy or intensity, which means that for every 3 dB (A) increase in sound, the same damage to one’s hearing is caused in half the time, and can cause permanent damage to a worker’s hearing twice as quickly.
LC,peak of 140 dB(C) means a worker cannot be exposed to a noise level above 140 decibels. Peak noise levels greater than 140 dB (C) usually occur with impact or explosive noise and can result in acoustic trauma injury (immediate and permanent hearing loss).
A noise assessment should also be conducted when changes have been made to the workplace, for example, installation of new or removal of old machinery, changes in workload or equipment operating conditions, or modifications in working arrangements, and where no previous noise level assessments have been conducted. Noise Assessments can be simple (for example, only involving a single noise source), or complex (for example, can involve multiple noise sources at variable noise levels). They should be conducted by a competent person such as an Acoustical Consultant or Occupational Hygienist, and in accordance with procedures stated in AS/NZS 1269.1:2005: Occupational Noise Management - Measurement and assessment of noise immission and exposure as advised in the SWA COP (2018). The more complex the situation, the more knowledgeable and experienced the person needs to be. There are many different types of noise measurement instruments available depending on the type of noise, and the purpose of the assessment.
Measure noise to answer key questions like:
Some indications that noise may be a problem in your workplace:
Step 1: Information Review
Before undertaking the Preliminary Assessment, revise all available and relevant information including current/previous Occupational Noise Management Programs (Hearing Conservation Programs), Noise emission data of plant utilized on site obtained from manufactures, Hazard/Risk Registers, Health Surveillance data (audiometric testing results to establish if any hearing loss or tinnitus have been noted during repeat testing, or if any worker compensation claims have been made for hearing loss), and any Previous Noise Assessments. To ascertain which workplace operations and procedures produce noise or may be contributing to the risk of hearing loss, consult with workers, and supervisors and observe job practices whilst walking around the workplace. Other factors to consider include exposure to ototoxic substances and vibration. Hearing loss can be exacerbated when noise is combined with some ototoxic substances and/or with vibration (particularly hand-arm vibration). Further information on ototoxic substances and vibration can be found in the SWA COP (2018) (Appendix B),as well as the AS/NZS 1236.0 (Appendix C).
Step 2: Preliminary Assessment
A Preliminary Assessment, often referred to as a 'walk through' audit or survey, are performed when no previous Noise Assessments have been conducted, or previous Noise Assessments are more than 5 years old. The main aim of a Preliminary assessment is to establish whether or not you have excessive noise in the workplace, and to help identify areas, equipment items, and/or job classifications where noise problems exist. All areas less than 80 dBA should be documented and identified as a low noise risk area. If noise levels are 80 dB (A) or more, or there is any doubt about whether noise levels are excessive, a Detailed Assessment is recommended and should be scheduled and conducted to fully assess the environment as soon as practical. A noise hazard identification checklist is provided in the SWA COP (2018) (Appendix C) to assist you further with this process.
Tip: Compose a drawing or sketch of the workplace to refer to during your Detailed Assessment.
Step 3. Detailed Assessment
A Detailed Assessment (or Detailed Noise 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 Detailed Assessments include:
Area and/or Machinery Noise Survey: Helps quantify the noise environment, create noise maps of area sound levels, and determine if a Noise Exposure 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 describe the noise levels for each area or job description.
Noise Exposure Survey: Involves gathering detailed information about specific job tasks, areas, or equipment. Results are useful to determine worker noise exposures, make hearing protection assignments, and identifying who is in or out of the HCP.
Noise Control Survey: Focuses on identifying and prioritizing options for reducing the noise hazard using engineering or administrative controls.
Step 4: Follow up Assessments
Ensure Assessments are updated as often as necessary to understand the current status of exposures in the workplace. Check that measurements and evaluations are performed in a manner that allows for comparison with previous assessments. Follow up assessments shall be carried out at least every five years, whilst supplementary assessments should be carried out, for example, after new plant and equipment has been introduced, where process or procedural changes have occurred or where seasonal or workload related factors may affect noise exposures.
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. AS/NZS 1269.1 - Occupational Noise Management - Measurement and Assessment of Noise Immission and Exposure, states that an integrating sound level meter of at least Class 2/Type 2 may be used for most HCP noise measurements, except in situations marginally above or below the WES or where high precision is required. A Class 1/Type 1 integrating sound level meter is the preferred instrument for measuring sound pressure levels and octave band filters fitted to SLMs must comply with Class 1/Type 1 requirements according to AS/NZS 4476 Acoustics—Octave-band and fractional-octave-band filters.
A non-integrating SLM will provide a reading of A-Weighted sound pressure level and should only be used for Preliminary Assessments where fluctuations of sound do not exceed 6 dB(A), and when measures are conducted in the ‘S’ time weighting mode.
Refer to AS/NZS1269.1 Occupational Noise Management-Measurement and assessment of noise immission and exposure for further information.
Measure and display the sound level in real-time. They do not average or store results.
In addition to measuring and displaying the sound levels, advanced SLMs can average, or integrate the sound levels over time. This is an important function because the risk of hearing loss and noise exposure limits are based on the average sound levels measured. These SLMs meters 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 throughout the work shift. At the end of the sampling period, the instrument automatically calculates the time-weighted average, noise dose, and other important metrics. Regulations require that employers 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 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.
Microphones are transducers that detect sound pressure and convert it into an electrical signal for subsequent processing. There are three types of microphones for occupational measurements. These include Random incidence microphones (omni-directional), Direct incidence microphones (free field), and pressure microphones (pressure response). For occupation noise measurements, the most commonly supplied microphone by SLM manufacturers is the random incidence or omni-directional microphone. Review manufacturers specification to confirm microphone type before device use.
Noise measurement instruments are categorised by Class or Type according to the accuracy of the microphones. Class 2/Type 2 general purpose instruments are designed to be accurate to +/- 2 dB .
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.
The results of a sound level survey depend on the measurement settings used. AS/NZS 1269.1 - Occupational Noise Management - Measurement and Assessment of Noise Immission and Exposure, specifies which settings should be used for compliance. The preferred basic measurement qualities as noted in AS/NZS 1269.1 are LAeq,T, or EA,T (during representative intervals) T and Lpeak. When a workers occupies one or more work locations LAeq,Ti or EA,Ti and Lpeak are recommended.
A – weighting
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.
C – weighting
The C-Weighting is predominantly used to measure peak sound pressure levels as well as determining the suitability of hearing protector devices in a particular work environment.
The decibel reading displayed on a sound level meter is an average of the sound level measured over a certain time which can be Fast, Slow or Impulse time weighted. For hearing conservation, a slow response setting (“S”) is used, meaning that the value on the display is the 1-second average that was measured while the instrument is on.
The 3 dB exchange rate is commonly used to describe the metric employed for worker noise exposure determinations. The concept is that a person can accumulate the same noise exposure during a nominal workday by exchanging lower noise levels for more exposure time, or conversely, exchanging higher noise levels for less exposure time.
Criterion level: 85 dB(A)
Upper limit: 140 dB(C)
Exchange Rate: 3 dB
Frequency weighting: A
Peak weighting: C
AS/NZS 1269.1 - Occupational Noise Management - Measurement and Assessment of Noise Immission and Exposure, suggests a maximum of 5 years between initial and follow-up noise monitoring. Duty holder’s are required to do supplementary noise surveys whenever there is a change in processes, procedures, or exposure time that may lead to changes in workers noise exposures. Some companies choose to conduct surveys periodically (e.g. every year or two) to ensure that all exposed workers are included in their hearing conservation programs.
To deal effectively with noise problems in the workplace, systematic investigation, planning, budgeting and implementation are necessary. The Safe Work Australia (SWA), Code of Practice (COP): Managing hazardous noise and preventing hearing loss at work’ (2018), and AS/NZS 1269.2 Occupational noise management – Noise control management, provide guidance on noise control management and outline strategies that should be implemented in both existing and proposed workplaces. A handy checklist is provided in AS/NZS 1269.2, (Section 3) and should be used when following the guidance on noise control management. The basic steps of a Noise Management Program (or Hearing Conservation Program) are outlined in AS/NZS 1269.0–2005 Occupational Noise Management – Overview and General Requirements.
Work Health and Safety Legislation in Australia limit a worker's noise exposure to LAeq,8h of 85 dB(A), referenced to 20 µ Pa (averaged over an 8-hour exposure) or C-Weighed peak sound pressure level of peak exposure of 140 dB(C) referenced to 20 Pa.
A 'persons conducting a business or undertaking' (PCBU) may choose proactive policies to better protect exposed workers. Best practices for noise measurement include:
Keep noise measurement data current by repeating surveys every one to two years. 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.
Conduct enough samples to ensure that the noise measurements are representative of the worker’s exposures. This may require a statistical sampling approach. Document areas and job tasks that have noise levels and/or exposures that are less than 80 dB(A) or 135 dB(C) as well as areas or job tasks where workers are regularly exposed to combinations of noise, ototoxic substances and/or vibration (mainly Hand and Arm).
Note: Research demonstrates exposure to ototoxicants (including certain pesticides, solvents, and pharmaceuticals) may cause hearing loss or balance problems, regardless of noise exposure.
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.
Consider contracting with a noise specialist for guidance and detailed assessment requests that go beyond the expertise of the 'persons conducting a business or undertaking' (PCBU). Engage workers in identifying noise problems and solutions.
Noise, SafeWork Australia
See “Codes and Guides” tab links to: Model Code of Practice: MANAGING NOISE AND PREVENTING HEARING LOSS AT WORK: October 2018.
This page also includes links to State and Territory Regulators for specific local requirements.
The Australian Standard AS/NZS 1269 series, Occupational noise management (1 – 4), provides technical requirements and guidance on all facets of occupational noise management.
IMPORTANT NOTE: This information is based on selected current national requirements. Other country or local requirements may be different. Always consult User Instructions and follow local laws and 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 laws and regulations must be followed.