ISO 3747:2010

Overview

ISO 3747:2010 - "Acoustics - Determination of sound power levels and sound energy levels of noise sources using sound pressure - Engineering/survey methods for use in situ in a reverberant environment" - specifies an in‑situ comparison method to determine the sound power level or sound energy level of machinery, equipment or sub‑assemblies. Measurements are made in a room where reflections from surfaces dominate (a reverberant environment) by comparing octave‑band sound pressure levels from the test source with those from a calibrated reference sound source. Results are produced in one‑octave bands (nominal 125 Hz to 8 000 Hz range) and can be combined to give A‑weighted sound power/energy levels.

Key technical topics and requirements

• Comparison method: Determine source sound power/energy by direct comparison with a calibrated reference sound source operated in the same room and positions.
• Frequency bands: Results calculated per one‑octave band (typical mid‑bands 125 Hz–8 000 Hz); A‑weighted totals derived from octave levels.
• Types of noise covered: Suitable for steady, non‑steady, fluctuating and isolated burst/transient noises (per ISO 12001 definitions); primarily for broadband sources but usable for narrow‑band/discrete tones (with possible reduced reproducibility).
• Test environment: Room where microphone sound pressure mainly depends on surface reflections (reverberant field). Background noise must be low relative to the source for engineering‑grade results.
• Accuracy and uncertainty: Guidance on measurement uncertainty is provided; reproducibility conforms to ISO 12001:1996 accuracy grade 2 (engineering) or grade 3 (survey) depending on how well environmental requirements are met.
• Instrumentation & positioning: Requirements for reference sound sources, microphone positions, measurement distance, background noise correction and calibration are addressed in the standard and its normative references.
• Annexes: Include rules for microphone/reference source placement, meteorological corrections, A‑weighting calculations, and guidance on uncertainty evaluation.

Practical applications - who uses ISO 3747:2010

• Acoustic engineers and test laboratories performing in‑situ noise surveys of stationary equipment and factory machinery that cannot be moved to a test chamber.
• Product compliance and environmental noise assessments where sound power/energy ratings are required for noise control, procurement, or regulatory reporting.
• R&D and maintenance teams quantifying noise from large installations, HVAC systems, compressors, pumps and other fixed plant items.

Related standards (normative and complementary)

• ISO 12001:1996 (noise test code rules), ISO 6926 (reference sound sources)
• Other ISO acoustics series: ISO 3740–ISO 3744, ISO 3741, ISO 9614 (alternative methods)
• Measurement/uncertainty: ISO/IEC Guide 98‑3 (GUM), ISO 5725
• Instrument standards: IEC 61672‑1, IEC 60942, IEC 61260

Keywords: ISO 3747:2010, sound power level, sound energy level, reverberant environment, in situ measurement, A‑weighted, octave bands, reference sound source, measurement uncertainty.