ISO 11205:2003

Overview - ISO 11205:2003 (Acoustics, Sound Intensity, In situ Measurements)

ISO 11205:2003 defines an engineering method (grade 2 accuracy) for determining the emission sound pressure level of machinery and equipment in situ using sound intensity measurements. It is intended as an alternative to ISO 11201, ISO 11202 and ISO 11204 for on-site tests and applies to equipment emitting stationary broadband noise, including cases with discrete frequency or narrow-band components. The method is valid in a wide range of test environments provided requirements on background noise and field indicators are met.

Key topics and technical requirements

• Measurement principle: Uses sound intensity to separate direct (source) sound from diffuse or reflected sound; sound intensity vector and pressure–intensity indicators are central concepts.
• Accuracy class: Engineering method with grade 2 accuracy suitable for practical in situ assessments.
• Instrumentation: Intensity probes and analysers must meet IEC 61043 class requirements; calibration traceable to standards is required. The probe’s residual pressure–intensity index must exceed the field indicator by a specified margin.
• Corrections and indices:
  • Hemi-free field intensity correction (K5): a small, frequency-independent correction (K5 = 1 dB) to account for floor reflection effects.
  • Bias error factor (K): used in defining dynamic capability index (K = 10 dB in this standard).
• Measurement procedure: Covers installation and operation of the source, defined specified positions (work station, bystander positions), measurement time intervals, frequency-band analysis (octave/1/3-octave), wind/gas-flow considerations, and criteria for qualifying a valid measurement.
• Uncertainty: Guidance on estimating measurement uncertainty and reference to statistical methods (ISO 7574-1 and GUM) and recommended reporting of repeatability/reproducibility.
• Annexes: Normative annexes cover adequacy of intensity vector direction (A), procedures for frequencies above 5 000 Hz (B), and actions if measurements fail to qualify (C); Annex D gives an example test table.

Applications and who uses it

ISO 11205 is used by:

• Acoustic consultants and test engineers performing on-site noise assessments of machinery.
• Manufacturers validating noise emission at workstations or at specified positions near equipment.
• Health & safety professionals and occupational hygienists assessing worker exposure and compliance.
• Certification bodies and laboratories conducting standardized in situ noise testing.

Practical uses include workstation noise evaluation, bystander position surveys, noise test code implementation, and comparative assessments when factory or field conditions preclude laboratory testing.

Related standards

• ISO 11201, ISO 11202, ISO 11204 (alternative in situ methods)
• ISO 7574-1 (statistical methods)
• IEC 61043 and IEC 60942 (instrumentation and calibration)

Keywords: ISO 11205:2003, sound intensity, emission sound pressure level, in situ measurements, machinery noise, acoustics, noise testing, IEC 61043.