Sound Meter Basics: What You Should Know
What is a Sound Meter?
A sound (noise) level meter measures sound pressure level in decibels (dB) using frequency weightings (A/C/Z) and time weightings (Fast/Slow). It’s used for workplace health and safety checks, environmental licence compliance and lab work. In Australia, the exposure standards are LAeq,8h 85 dB(A) and LC,peak 140 dB(C).
How a Sound Meter Works
A condenser microphone converts air pressure into voltage, a pre-amplifier and analogue-to-digital converter (ADC) digitise it, and onboard DSP computes descriptors like LAeq, LAFmax, and statistical levels (LAF10/LAF90). Many meters add octave/third-octave analysis and data logging. Meters are built to Class 1 (higher precision) or Class 2 tolerances; Class 1 is the usual choice for compliance and environmental monitoring in NSW.
Australian Standards & Regulatory Context
Work health & safety exposure standards (WHS): LAeq,8h 85 dB(A) and LC,peak 140 dB(C). The Code shows dose logic (e.g., 88 dB(A) for 4 h ≈ 85 dB(A) for 8 h).
Environmental compliance (NSW): NSW EPA Approved Methods (2022) require a Class 1 sound level meter conforming to AS/NZS IEC 61672.1:2019. The acoustic calibrator must comply with IEC 60942:2017 and be the same class as the meter.
Policy framework: The Noise Policy for Industry (2017) is the key guideline for industrial assessments in NSW.
Class 1 vs Class 2: Which Do You Need?
Class 1: tighter tolerance; required for NSW EPA licence/consent compliance and most formal environmental surveys.
Class 2: suitable for internal screening or preliminary OH&S checks; not acceptable for NSW EPA compliance submissions.
Core Measurements & Metrics
LAeq,T – time-averaged A-weighted level over period T.
LAFmax – highest A-weighted level with Fast time weighting.
LAF90 / LAF10 – A-weighted levels exceeded for 90%/10% of T (background vs. “loud” events). Where a licence doesn’t specify descriptors, the Approved Methods require at least LAeq,T, LAFmax, LAF90, LAF10 with 15-minute Fast as the default for statistical descriptors.
Quick lab example: If a packaging line returns LAeq,15min 82 dB(A), LAF90 78 dB(A) and LAFmax 93 dB(A), you’re seeing steady background around 78 dB(A) with intermittent peaks from events like capping
Calibration & Field Checks (What Good Practice Looks Like)
Field checks: Perform an acoustic calibrator check immediately before and after measurements. If the post-check differs by > 1.0 dB from the pre-check, disregard the intervening measurements and repeat.
Class-matched calibrator: Use a calibrator that meets IEC 60942:2017 and is the same class as your meter (Class 1 with Class 1).
Traceable lab calibration: The reference sound source (and other relevant instrumentation) must be calibrated by a NATA-accredited facility at least once every two years for environmental work. Keep certificates.
Metrological traceability: Follow NATA’s Metrological Traceability Policy under ISO/IEC 17025; certificates should state uncertainty and traceability.
Choosing a Sound Meter for Australian Use
Checklist
Class: Class 1 (AS/NZS IEC 61672.1:2019) for EPA/consent/licence work.
Frequency & dynamic range: Cover your sources (low-frequency plant noise to impulsive peaks).
Logging & descriptors: LAeq, LAFmax, LAF10/90; 1/3-octave option for tones/low-frequency checks.
Accessories: Class-matched IEC 60942:2017 calibrator, large windshield, tripod, weather kit, GPS/time-sync, and reporting software aligned to Approved Methods.
Compliance note: If measuring for NSW EPA licence compliance, confirm your meter and calibrator match the standard editions explicitly named in the Approved Methods.
Safety & Compliance Examples for Labs and Manufacturing
WHS exposure planning: The exposure standards are LAeq,8h 85 dB(A) and LC,peak 140 dB(C). Every +3 dB roughly halves allowable time (e.g., ~88 dB(A) for 4 h ≈ 85 dB(A) for 8 h). Use this for shift design and hearing protection programs.
Typical cases:
Cleanrooms/biotech filling: mid-70s to low-80s dB(A) → verify LAeq against task duration; ensure staff rotation if close to 85 dB(A).
Tablet presses: mid-80s to low-90s dB(A) at operator position → check daily patterns; confirm hearing protection class under AS/NZS 1269 program guidance referenced by the WHS Code.
Beverage bottling halls: mid-90s dB(A) with impulsive peaks → measure LC,peak and verify it stays < 140 dB(C).
When to Call an Accredited Cal Lab (And What You’ll Get)
Use a NATA-accredited (ISO/IEC 17025) facility for periodic instrument calibration (at least every two years for environmental-noise reference sources/instrumentation, or more often if your QMS requires). Expect a certificate with measurement uncertainty, traceability, equipment IDs, and results that regulators recognise.
CISCAL is NATA-accredited (No. 411) with national coverage (NSW, VIC, QLD). We calibrate sound level meters, calibrators and related accessories; our SMART Portal gives you asset histories, reminders and downloadable certificates.