Overview
ISO/TR 17534-4:2020 provides recommendations for a quality‑assured, verifiable software implementation of the sound propagation part of the CNOSSOS‑EU calculation method (COMMISSION DIRECTIVE (EU) 2015/996), in accordance with ISO 17534‑1. The technical report clarifies ambiguous aspects of CNOSSOS‑EU:2015, supplies a comprehensive set of illustrative test cases with reference solutions, and offers an example template for a declaration of conformity for software vendors. Note: source models and aircraft noise calculations are outside this document’s scope.
Key topics and technical requirements
- Standardized interpretation of CNOSSOS‑EU:2015 to ensure consistent software behavior across implementations.
- Detailed handling of ambiguous propagation issues, including:
- sloping objects and equivalent heights
- ground factors and spatially varying ground properties
- octave band treatment and centre frequencies
- diffraction (including lateral and retro‑diffraction) and Rayleigh’s criterion
- reflection on near‑vertical structures and complex object interactions
- distances and geometry conventions used in CNOSSOS‑EU equations
- A structured test-suite (TC01–TC28) covering flat and varying ground, barriers, buildings, long‑distance propagation and combinations of effects; each test case includes intermediate and final reference results for validation.
- Quality assurance guidance for software developers: documentation identification, agreed interpretations of ambiguous clauses, and a sample declaration of conformity to support compliance claims.
- Normative references include ISO 17534‑1, ISO/TR 17534‑2, and the COMMISSION DIRECTIVE (EU) 2015/996 (CNOSSOS‑EU:2015).
Applications and who should use it
- Acoustic software developers implementing outdoor sound propagation modules to ensure CNOSSOS‑EU compliance and interoperable outputs.
- Environmental consultants and noise modelers validating software and interpreting propagation results for strategic noise mapping.
- Regulatory bodies, local authorities and project auditors who need verifiable conformity checks for noise‑mapping tools under EU directives.
- QA engineers and test laboratories using the provided test cases and reference solutions to perform independent validation and regression testing.
Related standards
- ISO 17534‑1 - Quality requirements and quality assurance for outdoor sound calculation software
- ISO/TR 17534‑2 - General recommendations for test cases and QA interface
- COMMISSION DIRECTIVE (EU) 2015/996 - CNOSSOS‑EU:2015 (source method document)
ISO/TR 17534‑4:2020 is a practical resource for ensuring a quality‑assured implementation of CNOSSOS‑EU sound propagation in software, improving consistency and comparability of environmental noise assessments across organizations and EU Member States.