How do Noise Monitoring work?
A noise instrument converts sound pressure into an electrical signal with a calibrated condenser or MEMS microphone. The signal passes through frequency weighting filters, most commonly A-weighting that approximates human hearing, and C-weighting for peak and low-frequency content. A detector with exponential time weighting, Fast at 125 ms or Slow at 1 s, or an integrating stage produces the level in decibels relative to 20 µPa. Equivalent continuous level Leq, percentile levels such as L10 and L90, maximum and peak levels and sound exposure level are computed digitally. Class 1 instruments have tighter tolerances than Class 2 under IEC 61672-1. Octave or third-octave filter banks and FFT analysis add frequency information, and acoustic calibrators at 94 dB and 1 kHz check sensitivity. Permanent stations add weather protection and telemetry.
Which Noise Monitoring variants are available?
- Class 1 Integrating Sound Level Meter — A handheld precision instrument meeting IEC 61672-1 Class 1 that measures Leq, Lmax and statistical levels with frequency and time weightings.
- Personal Noise Dosimeter — A compact body-worn instrument that measures a worker's noise dose over a shift using a microphone at the shoulder, reporting Leq, TWA and percent dose.
- Permanent Outdoor Noise Monitoring Terminal — A weatherproof, continuously operating unit with a Class 1 or 2 microphone, telemetry and optional solar power for long-term noise monitoring at airports, construction sites, roads and industrial boundaries.
- Octave Band Sound Analyzer — A real-time analyzer that measures sound levels in 1/1 and 1/3 octave bands, often with FFT, for frequency-resolved noise assessment.
- Acoustic Calibrator for Sound Level Meters — A portable sound source that generates a stable tone, typically 94 dB at 1 kHz, to check and adjust the sensitivity of microphones and sound level meters.
How do I choose the right variant?
Choose the class and type according to the regulation: Class 1 for environmental noise assessment and legal evidence, Class 2 for general surveys and workplace screening. Decide between handheld meters for spot checks, dosimeters for worker exposure and permanent stations for continuous site monitoring. Check the level range, such as 20 to 140 dB, and whether the dynamic range covers both background and peak events. For industrial and product noise, frequency analysis in octave or third-octave bands is needed. Consider data storage, time-history logging with audio recording for source identification, IP rating, temperature range and battery life. For permanent installations, evaluate microphone protection, communication and power. Confirm that the supplier offers IEC 61672-3 periodic verification and traceable calibration.
Where are Noise Monitoring used?
Noise Monitoring are specified in community and environmental noise assessment, construction site noise compliance, occupational noise exposure surveys, industrial and product sound testing and airport and road traffic monitoring.
Which standards and certifications apply?
Work with Noise Monitoring is commonly governed by IEC 61672-1, IEC 61672-3, IEC 60942 (sound calibrators), ISO 1996-1, ISO 9612, IEC 61252 (personal exposure meters), GB 3096 and GB/T 3785.1. Instrument certifications such as CE marking are confirmed per configuration and never assumed.
What are the key considerations before purchase?
Calibrate with an acoustic calibrator before and after each measurement session and record any drift, which should be under 0.5 dB. Use a windscreen outdoors, keep the microphone 1.2 to 1.5 m above ground and at least 3.5 m from reflecting surfaces for free-field environmental measurements, and avoid rain or condensation on the capsule. Record weather conditions because wind above 5 m/s invalidates many measurements. Instruments need periodic verification in an accredited laboratory, typically every one to two years, following IEC 61672-3. Store in dry conditions, replace batteries before long campaigns, and preserve raw time history when regulators may audit the data. Permanent stations require protection from birds, vandalism and lightning.
