ISO 9614-2:1996

Overview - ISO 9614-2:1996 (Acoustics - Measurement by scanning)

ISO 9614-2:1996 specifies a method to determine sound power levels of noise sources using sound intensity measured by scanning. The standard requires measuring the component of sound intensity normal to a measurement surface that wholly encloses the source. The surface integral of this normal intensity gives the total sound power radiated into the air. Scanning may be performed manually or by mechanical systems; instruments record the segment-average normal intensity and averaged squared sound pressure.

Key topics and requirements

• Measurement principle: Sound power is obtained by integrating the normal component of the sound intensity over a closed measurement surface around the source.
• Scanning method: The measurement surface is subdivided into contiguous segments; an intensity probe scans continuously along specified paths to sample each segment (scan / scan-line density concepts defined).
• Frequency range & weighting: Current intensity probe limitations (IEC 1043) restrict measurements to the one-third‑octave range 50 Hz to 6.3 kHz. A-weighted band-limited sound power values are calculated from constituent octave or one-third‑octave band results (not by direct A-weighted intensity measurement).
• Quality indices and uncertainty: The standard defines ancillary tests and indices (e.g., pressure-residual intensity index, dynamic capability index) and classifies measurement uncertainty into grades (e.g., engineering (grade 2) and survey (grade 3)) based on ancillary results.
• Stationarity and environment: Signals must be stationary during segment measurements. The method is applicable in situ or in special-purpose environments that do not subject probes to excessive gas flows or rapidly varying extraneous noise.
• Limitations: Not suitable when measured band yields negative sound power or when extraneous outside sources, absorbing material inside the surface, or highly reactive/near fields compromise accuracy.

Applications and practical value

• Determining in-situ sound power levels of machinery and equipment where traditional pressure-based ISO methods (ISO 3740–3747) are impractical.
• Testing large installations or equipment that cannot be placed in special low-noise facilities.
• Field surveys, product development, noise control engineering, environmental noise assessment, and verification of noise-reduction measures.
• Useful when extraneous noise or facility constraints make pressure-based methods unsuitable.

Who uses this standard

• Acoustic consultants and noise control engineers
• Test laboratories and compliance teams
• Manufacturers of industrial machinery and large equipment
• Environmental noise analysts conducting in-situ measurements

Related standards

• ISO 9614-1 (discrete points method) and ISO 9614-3 (precision scanning) - complementary methods in the ISO 9614 series.
• IEC 1043 - instrument requirements for intensity probes referenced by ISO 9614-2.

Keywords: ISO 9614-2, sound power level, sound intensity, intensity scanning, acoustics standard, in-situ testing, one-third-octave, A-weighted sound power.