If you're shopping for a sound level meter, one of the first questions you'll encounter is: Class 1 or Class 2? Understanding the difference is essential for choosing the right instrument for your application — and for ensuring your measurements meet regulatory requirements.
What Do Class 1 and Class 2 Mean?
The classification system comes from IEC 61672, the international standard for sound level meters. It defines two performance classes based on measurement accuracy and tolerance limits:
- Class 1 (Type 1): Higher accuracy, tighter tolerances. Required for precision measurements, legal proceedings, and regulatory compliance in many jurisdictions.
- Class 2 (Type 2): Slightly wider tolerances, but still suitable for most field measurements, occupational noise surveys, and general environmental monitoring.
Key Differences at a Glance
- Accuracy: Class 1 has tighter frequency response tolerances (±1.1 dB at 1 kHz) vs Class 2 (±1.4 dB at 1 kHz)
- Temperature range: Class 1 instruments typically operate over a wider temperature range
- Price: Class 1 instruments are generally more expensive due to higher manufacturing precision
- Applications: Class 1 for legal/regulatory work; Class 2 for routine surveys and screening
When Do You Need Class 1?
Choose a Class 1 sound level meter when:
- Your measurements may be used as legal evidence or in noise nuisance disputes
- Local regulations specifically require Class 1 instruments (common in environmental impact assessments)
- You need the highest possible measurement accuracy for research or calibration purposes
- You're performing building acoustics measurements to ISO 16283 or similar standards
When Is Class 2 Sufficient?
Class 2 is appropriate for:
- Occupational noise assessments under ISO 9612 — the standard explicitly permits Class 2 instruments for most workplace measurements
- Routine environmental noise screening and monitoring
- Construction noise monitoring where high precision is not required
- General industrial noise surveys
- Educational and training purposes
What About the Microphone?
The sound level meter classification also depends on the microphone. A Class 1 instrument requires a Class 1 microphone (IEC 61094 WS1 or equivalent). Using a Class 2 microphone on a Class 1 meter body effectively downgrades the system to Class 2 performance.
Our Recommendation
For most occupational health and safety professionals, environmental consultants, and industrial hygienists in Asia, a Class 2 sound level meter with data logging and octave band analysis is the most practical and cost-effective choice. If you regularly work on projects requiring legal defensibility or environmental impact assessments, invest in a Class 1 instrument.
At Placid Asia, we stock both Class 1 and Class 2 sound level meters with full technical support and ISO/IEC 17025 accredited calibration. Browse our sound level meter range or contact us for instrument selection advice.