ISO/PAS 1996-3:2022

Overview

ISO/PAS 1996-3:2022 - "Acoustics - Description, measurement and assessment of environmental noise - Part 3" defines an objective method to measure the prominence of impulsive sounds and to determine an adjustment to L_Aeq (equivalent continuous A-weighted sound level). The method is intended to correlate measured impulsive characteristics with community response for environmental noise assessment. It is not intended for firearms, high‑energy impulsive sources (per ISO 1996‑1) or occupational hearing-loss assessments.

Key topics and technical requirements

• Prominence (P): An index combining the impulse onset rate and level difference to quantify how prominent an impulse is at the receiver. The general form is P = k1·log(onset rate) + k2·log(level difference); constants are derived from listening tests.
• Onset rate and level difference: Onset rate (OR) is calculated from the slope of the A‑weighted, F‑time-weighted level (threshold: gradients ≥ 10 dB/s define an onset). Level difference (LD) is the difference between onset start and end.
• Measurement instrumentation: Uses Class 1 sound level meters (IEC 61672‑1) with logged A‑weighted, F‑time‑weighted samples. Preferred sampling interval is 10–25 ms; 100 ms is allowed for screening with higher uncertainty.
• Assessment time interval: Default is 30 minutes. The impulse with the highest P during each interval provides the adjustment for that interval; reference-time ratings are energy-averages of assessment intervals.
• Adjustment to L_Aeq: The standard defines how to convert prominence into a penalty/adjustment applied to L_Aeq (typical adjustments are in the range 0.0 dB to 9.0 dB). These adjustments are used to categorise sources (regular impulsive vs. highly impulsive) per ISO 1996‑1, or may be applied directly as in some national methods.
• Data handling: Guidance on excluding residual-source impulses, use of audio recording for unattended surveys, and reporting requirements is included.
• Research guidance: Annex A lists recommended research topics where further work is needed.

Practical applications

• Quantifying impulsive environmental noise from industrial processes, goods handling, demolition tools, compressed-air releases, skateboard ramps, powered riveting, fork lifts, etc.
• Providing an objective basis for applying impulsivity penalties to L_Aeq in environmental noise assessments, planning decisions, nuisance investigations, and impact assessments.
• Supporting noise mitigation planning, regulatory enforcement and community response studies by linking measurable impulse characteristics to annoyance.

Who should use this standard

• Acoustical consultants and environmental noise specialists
• Local authorities and planning regulators
• Industrial noise control engineers and site operators
• Researchers studying noise annoyance and impulsive sound metrics

Related standards

• ISO 1996‑1 (basic quantities and assessment procedures)
• ISO 1996‑2 (measurement guidance)
• IEC 61672‑1 (sound level meter specifications)
• Related national methods: BS 4142, NT ACOU 112

Keywords: ISO 1996-3:2022, environmental noise, impulsive sounds, prominence, L_Aeq adjustment, onset rate, level difference, sound level meter, Class 1.