Overview
EN ISO 3745:2012 (ISO 3745:2012) - “Acoustics - Determination of sound power levels and sound energy levels of noise sources using sound pressure - Precision methods for anechoic rooms and hemi-anechoic rooms” - defines laboratory precision methods to determine sound power levels and sound energy levels from sound pressure measurements in anechoic and hemi-anechoic test rooms. The standard specifies test-room qualification, instrumentation, microphone arrays, measurement surfaces (spherical and hemispherical), test procedures and reporting, and guidance on measurement uncertainty. It supersedes the 2003 edition and includes provisions relevant to EU Directive 2006/42/EC (Machinery Directive).
Key Topics and Requirements
- Test room criteria: acoustic adequacy, background-noise limits and temperature control for anechoic and hemi-anechoic rooms.
- Instrumentation: specifications for acoustical and meteorological instruments used during tests.
- Source installation & operation: guidance on mounting, auxiliary equipment and positioning of noise sources.
- Measurement surfaces: spherical (anechoic) and hemispherical (hemi-anechoic) measurement surfaces and associated microphone arrays.
- Microphone positions: normative arrays and path layouts for consistent sound pressure sampling (see multiple annexes for array geometries).
- Calculations: determination of sound power and sound energy levels (steady, non‑steady and impulsive noise), directivity indices, surface non‑uniformity indices, and frequency-weighted results.
- Measurement uncertainty: methodology for estimating combined and expanded uncertainty, with informative guidance and typical upper-bound values.
- Documentation: required test information and standardized test report content to ensure traceability and conformity.
Applications
- Laboratory acoustic testing of machinery, equipment and components to quantify emitted noise.
- Compliance testing for product standards and regulatory frameworks (e.g., Machinery Directive 2006/42/EC).
- Supplier and in-house noise-acceptance testing, R&D noise characterization, and certification by accredited test houses.
- Development of noise-control solutions and verification of noise mitigation measures.
Who Uses This Standard
- Acoustic test laboratories and calibration facilities
- Manufacturers and product engineering teams performing noise declarations
- Acoustic consultants and researchers conducting precision sound power/energy measurements
- Certification and conformity assessment bodies
Related Standards and Guidance
- Prepared by ISO/TC 43 (Acoustics). This edition replaces ISO 3745:2003.
- Includes normative annexes for room qualification, microphone arrays and calculation methods, plus an informative annex linking the standard to EU regulatory requirements (Annex ZA).
Keywords: EN ISO 3745:2012, ISO 3745, acoustics, sound power level, sound energy level, anechoic room, hemi-anechoic room, sound pressure, measurement uncertainty, microphone array.
