Field-ready measurement techniques for environmental, occupational, and building acoustics using HBK Class 1 sound level meters and array systems. Covers instrument selection, weighting and time response, building acoustics workflows, and the practice that makes a report defensible.
What’s Covered
Why class matters: IEC 61672 explained
IEC 61672 defines two classes of sound level meter. Class 1 instruments meet tighter tolerances on frequency response, directional response, level linearity, time weighting, and overall accuracy than Class 2 instruments. The choice between classes is rarely a matter of preference, it is dictated by what the report will be used for.
- Environmental compliance against bylaws or regulations: typically Class 1 required
- Workplace noise exposure under ISO 9612 or local OHS regulation: Class 1 or Class 2 depending on jurisdiction
- Building acoustics under ISO 16283: Class 1 required
- Product comparison for internal R&D: Class 1 strongly recommended for defensible repeatability
- Indicative survey or troubleshooting: Class 2 acceptable
Durham Instruments stocks the HBK Class 1 sound level meter range, see the sound level meters & vibration meters catalog.
HBK sound level meter families
| Instrument | Best fit | Notable features |
|---|---|---|
| HBK 2245 | Compact Class 1 with task-tailored Partner apps | Work, Environmental, and Exhaust Noise variants; smartphone integration |
| HBK 2250 / 2250-S Light | Basic Class 1 occupational, environmental, and product measurement | Compact, rugged, expandable analyzer |
| HBK 2255 | Single-channel Class 1 with mobile and PC app integration | Modern interface, broad task support |
| HBK 2270 / 2270-S | Two-channel Class 1 advanced analyzer | Sound intensity, building acoustics, comprehensive analysis |
Most teams standardize on a single instrument family and add complementary devices only when a specific application demands it. Mixing instrument types within one campaign creates documentation work that rarely pays back.
Three measurement types and what each requires
Environmental noise (ISO 1996)
Outdoor measurements typically span longer time windows and require weather correction (wind speed and direction, temperature, precipitation). Use a windscreen, document weather throughout, and exclude periods affected by extreme conditions per the standard.
Occupational and workplace noise (ISO 9612)
Workplace measurements characterize exposure across a worker’s shift. Personal noise dosimeters or sampling-based fixed measurements both apply; the standard prescribes which is appropriate. Document task durations and source locations.
Building acoustics (ISO 16283)
Reverberation time, sound insulation, and impact noise measurements use a controlled source (loudspeaker or tapping machine) and dual-channel analysis. The HBK 2270-S is the standard tool for this work and is the source of most defensible Canadian building acoustics reports.
Weighting, time response, and integration
Three settings define the level you record. Get them wrong and the result is unanswerable.
- Frequency weighting: A-weighting is the default for human-perceived loudness and most regulations; C-weighting captures low-frequency content more faithfully; Z (linear) weighting is unweighted
- Time weighting: Fast (125 ms) and Slow (1000 ms) define the integration time of the displayed level; Impulse is for transient sources but is rarely the right choice in modern work
- Integration period: Leq averages level over a defined window; Lmax and Lmin report extremes; Ln percentile statistics describe distribution
Document which combination was used for each measurement. Reports that omit weighting and integration are routinely rejected on review.
Field workflow that produces defensible reports
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Calibrate before and after
Use a Class 1 sound calibrator (typically 94 dB or 114 dB at 1 kHz) at the start and end of every measurement session. Record both readings; flag drift greater than the manufacturer’s tolerance.
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Document the geometry
Microphone height, distance from the source, distance from reflecting surfaces, and orientation. A well-photographed setup shortens any future review.
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Use a windscreen outdoors
Always. Wind noise contaminates low-frequency content and can dominate the broadband level on an exposed mic.
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Capture environmental conditions
Temperature, humidity, wind speed and direction, and atmospheric pressure. Weather logs are part of any environmental report.
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Annotate during capture
Note source events (vehicles, machinery transitions, voice activity) live so they can be excluded or included in post-processing per the standard.
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Validate before leaving
Inspect for clipping, dropouts, and obvious contamination. A 30-minute remeasurement on site is far cheaper than a return visit.
Field calibration is not laboratory calibration. Sound calibrators verify acoustic level at a known reference. Periodic laboratory calibration of the SLM and microphone, typically annual, is still required, and is documented separately on the instrument’s calibration certificate.
Post-processing with Measurement Partner Suite
HBK’s Measurement Partner Suite (and BK Connect for advanced analysis) is the standard post-processing platform for the 2245, 2250, 2255, and 2270 families. Capabilities relevant to most reports include octave and 1/3-octave analysis, FFT, audio playback for event identification, statistical reporting (Ln percentiles), and template-driven report generation that aligns with the most common standards.
Pair the SLMs with weather station kits, calibration accessories, and protective cases, all available in the Durham Instruments catalog, for a complete field-ready system.
FAQ
What is the difference between Class 1 and Class 2 sound level meters?
Class 1 instruments meet tighter tolerances under IEC 61672 than Class 2, particularly on frequency response, directionality, and linearity. Class 1 is generally required for environmental compliance, building acoustics, and most product certification work. Class 2 is acceptable for indicative surveys and some workplace measurements depending on jurisdiction.
Do I need to calibrate my sound level meter every time I use it?
Yes, at least at the start and end of every measurement session, using a Class 1 sound calibrator. This verifies the acoustic level path. It does not replace periodic laboratory calibration of the SLM and microphone, which is typically annual.
When should I use A-weighting vs. C-weighting?
A-weighting reflects human perception of loudness across the audible band and is the default for most regulations and occupational measurements. C-weighting is flatter at low frequencies and is used where low-frequency content matters, peak measurements, blast noise, and some impulsive sources.
What is Leq and why is it the most-reported metric?
Leq is the equivalent continuous sound level over a defined time window. It represents the steady level that would deliver the same total acoustic energy as the actual fluctuating signal. Most environmental and occupational standards specify Leq over a defined integration period because it correlates well with human exposure and bylaw frameworks.
Does Durham Instruments calibrate sound level meters?
Yes. Durham Instruments offers traceable calibration of acoustic instruments through OEM laboratories and qualified partners, with documented uncertainty and traceability suitable for ISO 9001 and audit requirements.
Planning an acoustic measurement campaign?
Talk to a Durham Instruments engineer about Class 1 instrumentation, calibrators, weather kits, and reporting workflows for environmental, occupational, and building acoustics.