Sound Level Meter
A sound level meter (SLM) is a calibrated electronic instrument that measures sound pressure level in decibels (dB), typically using A-weighting and slow response for occupational noise assessment. In Canada, it must meet at least Type/Class 2 performance requirements per IEC 61672-1 or ANSI S1.4, as specified by WorkSafeBC and federal regulations. It is used for spot measurements, noise mapping, and verifying compliance with exposure limits like 85 dBA Lex and 140 dBC peak.
On a manufacturing shop floor, a compliant sound level meter is used to conduct baseline noise surveys, identify noisy areas and equipment, and verify regulatory limits such as 85 dBA Lex (8-hour exposure) and 140 dBC peak for impact noise. The meter must be Class/Type 2 or better, with A-weighting and slow response. Measurements are taken at ear height near worker positions, using integrating modes for Leq over representative intervals. Results support hearing conservation programs, engineering controls, and SafeDesk documentation. Pre-use field calibration with an acoustic calibrator is mandatory, and data must be recorded under normal working conditions.
- Using non-compliant or uncertified instruments like Class 3 meters or consumer decibel apps, which are not recognized by WorkSafeBC or federal regulations, leading to invalid surveys and potential penalties.
- Incorrect weighting and response settings, such as using C-weighting or fast response instead of A-weighting and slow response for occupational noise measurements, misrepresenting exposure and jeopardizing compliance documentation.
- Poor measurement technique and documentation, including failure to calibrate before/after surveys, measuring in atypical conditions, or not recording exposure duration and equipment state, resulting in unreliable data and difficulty defending decisions.
What minimum technical specifications must a sound level meter meet for WorkSafeBC-compliant occupational noise surveys?
Based on WorkSafeBC guidance and CSA Z107.56, the meter must be Class 2 or better, compliant with ANSI S1.25-1991, IEC 651, IEC 61672-1, or ANSI S1.4. It must have A-weighting for dBA measurements, C-weighting for peak/impact noise (140 dBC limit), crest factor capability ≥ 30 dB, minimum dynamic range ≥ 50 dB, threshold adjustable to 75 dB or lower, and support slow response for regulatory measurements.
How do integrating sound level meters differ technically from non-integrating ones, and when should each be used?
Non-integrating SLMs measure instantaneous sound levels for spot/area surveys, while integrating SLMs calculate equivalent continuous sound level (Leq) over defined periods, useful for fluctuating noise. Integrating meters are recommended for formal noise surveys where tasks vary, feeding directly into Lex/TWA calculations. Dosimeters are preferred for mobile workers with complex exposure patterns.
What are the exposure limits that SLM measurements must be evaluated against in a WorkSafeBC context?
The daily noise exposure limit is 85 dBA Lex (8-hour equivalent), with measurement required when exposure may exceed 82 dBA Lex. The peak impact noise limit is 140 dBC. Federal workplaces use A-weighted sound pressure level with slow response for signage thresholds (e.g., permanent signs above 87 dBA).