Overview
EN ISO 9614-2:1996 - Acoustics: Determination of sound power levels using sound intensity - Part 2: Measurement by scanning specifies a practical, in‑situ method to determine the sound power of a noise source by measuring the normal component of sound intensity over a surface that encloses the source. The method approximates the surface integral of normal intensity by subdividing the measurement surface into segments and scanning an intensity probe continuously over each segment. Measurements (average normal intensity and averaged squared sound pressure per scan) may be taken manually or with mechanized scanning.
Key topics and technical requirements
- Measurement surface and segmentation: choose a surface that fully encloses the source; divide it into contiguous segments for scanning.
- Scanning procedure: continuous probe movement across each segment; scan-line density and probe speed affect sampling error.
- Measured quantities: segment-average normal sound intensity and averaged squared sound pressure (octave or one‑third‑octave bands). Band‑limited A‑weighted results are derived from these band values.
- Stationarity requirement: source and any significant extraneous sounds must be temporally stationary for valid results.
- Error sensitivity: method is sensitive to extraneous sources outside the measurement surface, reactive/near-field conditions, and high local pressure/intensity angle differences.
- Quality indicators and indices: the standard defines ancillary tests and indices (for example, the pressure‑residual intensity index φ and the dynamic capability index Ld) used to indicate measurement quality and classify the grade of accuracy.
- Frequency and equipment limits: the method relies on intensity measurement equipment (see IEC 1043) and practical frequency limits noted in the standard (limitations on low/high bands are discussed).
- Limitations: not applicable in frequency bands where measured sound power is negative, or where extraneous noise or gas flows exceed instrument capability.
Applications - who uses it
- Acoustic engineers and consultants for on‑site sound power determination of machines and installations.
- Manufacturers and test laboratories needing in‑situ evaluation where reverberation or anechoic facilities are impractical or when extraneous noise prevents traditional pressure‑based methods.
- Noise control and environmental specialists assessing equipment noise for compliance, product development, or noise abatement planning.
- Useful when ISO 3740–3747 pressure‑based methods are unsuitable due to facility constraints or high background noise.
Related standards
- EN ISO 9614-1 and EN ISO 9614-3 (other sound‑intensity methods)
- ISO 3740–3747 series (sound power from sound pressure methods)
- IEC 1043 (instruments for sound intensity measurement)
- IEC 942 (sound calibrators)
Keywords: EN ISO 9614-2, sound power, sound intensity, measurement by scanning, acoustics, noise measurement, in‑situ sound power, IEC 1043, acoustic testing.
