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CSA Z107.56-18: Measurement of Noise Exposure in Occupational Settings
Key requirements and implementation guidance for workplace noise measurement
Scope and Application
CSA Z107.56-18, titled Measurement of Noise Exposure, establishes a uniform methodology for assessing occupational noise exposure in Canadian workplaces. The standard applies to all workers whose noise exposure may reach or exceed the lower exposure action value (LEAV) of 80 dBA Lex,8h. It is intended for use by employers, occupational hygienists, and acoustical consultants to determine whether workers are exposed to noise levels that could cause hearing loss.
The standard recognizes three primary measurement strategies:
- Full-day measurement – continuous dosimetry over the entire work shift, suitable for jobs with highly variable noise.
- Representative task-based measurement – using a sound level meter to measure sound levels during specific tasks and then calculating the shift exposure from time-weighted averages.
- Questionnaire-based screening – an initial identification approach for workers whose exposure is likely below the action value.
Technical Requirements
Instrumentation
All instruments used for noise exposure measurement must conform to international performance standards. Sound level meters shall meet at least Class 2 requirements of IEC 61672-1:2013, while noise dosimeters must comply with IEC 61252. Acoustic calibrators used for field verification must satisfy Class 1 requirements of IEC 60942. Table 1 summarizes the key instrumentation requirements.
| Parameter | Requirement |
|---|---|
| Sound level meter standard | IEC 61672-1 Class 2 or better |
| Dosimeter standard | IEC 61252 |
| Frequency weighting | A-weighting (dBA) |
| Time weighting | Slow (1 s) or Fast (0.125 s) |
| Measurement range | 40–130 dBA |
| Calibrator accuracy | Class 1 per IEC 60942 |
| Field calibration check | Before and after each measurement series |
Measurement Strategy
The choice of strategy depends on the variability of the work and the resources available. For full-day measurements, the worker wears a dosimeter for the entire shift. Task-based measurements require identifying distinct noise tasks and measuring the sound level for each, along with the time spent on each task. The questionnaire method is reserved for low-exposure scenarios and must be validated with periodic spot checks.
Calculation of Exposure
The exposure metric is the A-weighted equivalent continuous sound level normalized to an 8-hour workday, expressed as Lex,8h. Calculations use a 3 dB exchange rate (i.e., doubling of sound energy doubles the exposure dose). The standard provides detailed formulas for combining partial exposures from different tasks or measurement intervals.
Uncertainty
CSA Z107.56-18 requires that measurement uncertainty be evaluated and reported following the principles of the ISO/IEC Guide 98-3 (GUM). Sources of uncertainty include instrument errors, positioning effects, and sampling strategies. A typical combined standard uncertainty for careful full-shift dosimetry is about 1 dB, leading to an expanded uncertainty (k=2) of ±2 dB. This uncertainty must be considered when comparing results to regulatory exposure limits.
Implementation Highlights
Implementing CSA Z107.56-18 involves the following recommended steps:
- Identify workers at risk – review job roles and previous exposure data.
- Select measurement method – choose between full-shift dosimetry, task-based, or screening.
- Prepare instruments – verify calibration and set appropriate parameters (e.g., A-weighting, exchange rate).
- Collect data – follow protocols for microphone placement (e.g., on shoulder near the ear), duration, and documentation.
- Calculate Lex,8h – use the equations in the standard to compute the normalized exposure.
- Compare to limits – apply the exposure action values (LEAV: 80 dBA, UEL: 85 dBA) in conjunction with the measured uncertainty.
- Report results – include the measurement method, instrument details, calibration records, and uncertainty statement.
Success: Following the steps above consistently improves the reliability of your noise exposure data and helps demonstrate due diligence in hearing conservation programs.
Tip: For jobs with high mobility or fluctuating noise, a noise dosimeter worn for the entire shift is the most representative method to capture the true exposure.
Compliance Notes
While CSA Z107.56-18 is technically a voluntary consensus standard, many Canadian occupational health and safety regulations (e.g., those in Ontario, British Columbia, and under the Canada Labour Code) reference it as the recommended method for measuring noise exposure. Compliance with the standard can therefore become de facto mandatory for organizations that are required to meet these regulations.
Warning: Always account for measurement uncertainty when comparing results to exposure limits. A measured Lex,8h of 82.5 dBA with an expanded uncertainty of ±2 dB means the true exposure could be above or below the 80 dBA action value.
The standard is technically equivalent to ISO 9612:2009 with some national deviations (e.g., the exchange rate is fixed at 3 dB, and specific Canadian action values are used). Organizations that operate across multiple jurisdictions may benefit from aligning their noise measurement programs with CSA Z107.56-18 to simplify compliance efforts.
Danger: Neglecting pre- and post-calibration checks can introduce errors of several decibels, potentially causing an underestimation of risk and leading to inadequate hearing protection for workers.
Training of personnel is essential. The standard recommends that those performing measurements be familiar with the principles of acoustics, instrument operation, and uncertainty evaluation. Regular internal audits and participation in inter-laboratory comparisons can further ensure measurement quality.
Frequently Asked Questions
Q: What exchange rate does CSA Z107.56-18 use?
A: The standard uses a 3 dB exchange rate (also known as the equal-energy rule). This means that a 3 dB increase in sound level results in a doubling of the noise dose, and a 3 dB decrease halves the dose.
A: The standard uses a 3 dB exchange rate (also known as the equal-energy rule). This means that a 3 dB increase in sound level results in a doubling of the noise dose, and a 3 dB decrease halves the dose.
Q: Is CSA Z107.56-18 legally required in Canada?
A: The standard itself is voluntary, but it is cited in many provincial and federal occupational health and safety regulations as the recognized method for noise exposure measurement. In practice, compliance often requires following the standard’s requirements.
A: The standard itself is voluntary, but it is cited in many provincial and federal occupational health and safety regulations as the recognized method for noise exposure measurement. In practice, compliance often requires following the standard’s requirements.
Q: How does CSA Z107.56-18 relate to ISO 9612?
A: CSA Z107.56-18 is harmonized with ISO 9612:2009 (Acoustics — Determination of occupational noise exposure — Engineering method). The Canadian standard includes additional national provisions, such as the defined exchange rate and specific action values for the Canadian regulatory context.
A: CSA Z107.56-18 is harmonized with ISO 9612:2009 (Acoustics — Determination of occupational noise exposure — Engineering method). The Canadian standard includes additional national provisions, such as the defined exchange rate and specific action values for the Canadian regulatory context.
Q: Can I use a sound level meter instead of a noise dosimeter?
A: Yes, the standard allows both instruments. Sound level meters are used for task-based measurements where the worker’s job consists of a number of discrete activities with known durations. For jobs with highly variable noise, continuous dosimetry is recommended to capture the full exposure footprint.
A: Yes, the standard allows both instruments. Sound level meters are used for task-based measurements where the worker’s job consists of a number of discrete activities with known durations. For jobs with highly variable noise, continuous dosimetry is recommended to capture the full exposure footprint.
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