Sound Level Meters

Class 1 and Class 2 are accuracy classifications defined by IEC 61672-1. Class 1 meters hold a tighter tolerance across a wider frequency range and are required where legally defensible or highly precise measurement is needed — regulatory noise disputes, product certification testing. Class 2 meters have a relaxed tolerance that's still accurate enough for general workplace noise surveys and most OSHA compliance work, at a lower cost.

A-weighting applies a frequency-dependent correction curve that approximates how the human ear perceives loudness at different frequencies, de-emphasizing very low and very high frequencies relative to the mid-range. Nearly all occupational and environmental noise standards specify A-weighted measurement (dBA) because it correlates better with perceived loudness and hearing damage risk than an unweighted reading.

A basic sound level meter gives an instantaneous or short-term reading, useful for spot checks. An integrating meter calculates the equivalent continuous sound level (Leq) over a set period, which is what occupational noise dose calculations and environmental compliance reporting under standards like ISO 9612 actually require. If you need to document an 8-hour work shift or a full night's environmental noise, you need integration and logging.

Field calibration with an acoustic calibrator (generating a known reference tone, typically 94 dB or 114 dB) should be done immediately before and after each measurement session to verify the meter hasn't drifted. Separately, the instrument itself typically needs full laboratory recalibration and certification annually to remain valid for regulatory use.

Most general industrial and workplace surveys fall within a 30-130 dB range, which covers everything from a quiet office to loud machinery without clipping. Confirm the expected peak levels of the specific equipment or process being measured — impact or impulse noise sources may need a meter with a higher peak-hold range and C-weighting capability.