Overview - ISO 13474:2009 (Acoustics, impulsive sound)
ISO 13474:2009 defines a practical engineering framework for calculating a statistical distribution of sound exposure levels from high‑energy impulsive sound events for environmental noise assessment. It applies to long‑range propagation (roughly 0.5 km to 30 km) from sources such as mine blasting, artillery fire and bomb explosions using moderate charge masses (≈ 0.05 kg to 1 000 kg TNT equivalent). The standard explicitly considers meteorological effects (refraction, turbulence, directed sound speed, atmospheric absorption) and terrain/ground effects on sound propagation. It is intended for environmental noise assessment - not for evaluating structural damage or injury risk.
Key topics and technical requirements
- Statistical distribution of single‑event sound exposure levels: method to derive distributions by combining source descriptors with propagation models across many replica atmospheres.
- Propagation physics covered:
- Geometric divergence and distance attenuation
- Atmospheric absorption and classification (atmospheric‑absorption classes)
- Excess attenuation due to refraction, turbulence, ground reflection and terrain shielding
- Directed sound speed profiles and atmospheric stability effects
- Terminology and equations: definitions for directed sound speed, band and frequency‑weighted sound exposure levels, long‑term average single‑event exposure and equivalent levels from multiple events.
- Probability of occurrence: procedures to assign weights to replica atmospheres using measurements, weather station data, or similarity relationships for the atmospheric surface layer.
- Classification and lookup tables: guidance on classifying atmospheric absorption and excess attenuation for practical calculations.
- Uncertainty: identification and treatment of measurement and modelling uncertainties (annexes include worked examples and uncertainty guidance).
Practical applications and users
ISO 13474:2009 is used when impulsive sounds travel over large distances and environmental noise impact needs quantification. Typical users:
- Acoustic consultants and environmental engineers assessing blast or military range noise impacts
- Mining and quarrying companies evaluating blasting noise at nearby communities
- Defense range managers modelling artillery and ordnance sound immission
- Regulators and planning authorities setting noise limits or assessing compliance
- Researchers studying long‑range impulsive sound propagation and meteorological coupling
Practical outputs include distributions of event sound exposure levels, long‑term averaged immission metrics (weighted by occurrence probabilities), and inputs for environmental impact statements.
Related standards
- ISO 1996‑1 (environmental noise descriptors)
- ISO 9613‑1 / ISO 9613‑2 (atmospheric absorption and outdoor propagation)
- ISO 17201 series (shooting range noise)
- ISO/IEC Guide 98‑3 (GUM: uncertainty)
Keywords: ISO 13474:2009, acoustics, impulsive sound, sound exposure levels, environmental noise assessment, blast noise, atmospheric absorption, sound propagation.