ISO 13347-2:2004

Overview

ISO 13347-2:2004 - “Industrial fans - Determination of fan sound power levels under standardized laboratory conditions - Part 2: Reverberant room method” - specifies a laboratory method for measuring the sound power levels of industrial fans using a reverberant room. The standard defines test environments, instrumentation and procedures (based on a reference sound source (RSS) substitution method) to produce engineering‑grade sound power data in one‑third octave bands. It is intended for standardized laboratory conditions and is not a field/site test method.

Key topics and technical requirements

• Reverberant room qualification: Test rooms must meet the qualification criteria given in Annex A (broad‑band sources) and Annex B (narrow‑band/pure tones) before use.
• Substitution method with RSS: Sound power of the fan is determined by substituting measurements from a calibrated reference sound source (RSS) and comparing measured sound pressure levels.
• Measurement quantities: One‑third octave sound pressure levels at prescribed microphone positions or along specified paths, plus fan aerodynamic data (rotational speed, pressure, flowrate).
• Test configurations: Covers the four ISO 5801 installation types - A (free inlet/free outlet), B (free inlet/ducted outlet), C (ducted inlet/free outlet) and D (ducted inlet/ducted outlet) - and allows for tests of fan inlet, outlet and casing sound power.
• Instrumentation & calibration: Instrumentation requirements are referenced to ISO 13347-1 and related ISO acoustics standards; the RSS must be calibrated and maintained.
• Limitations: Not intended for in‑situ measurements (increased uncertainty); vibration effects are not measured; reverberant tests generally require the test object to be <2% of room volume.
• Frequency resolution & uncertainty: Measurements are specified in one‑third octave bands and are of engineering grade uncertainty in accordance with ISO 3740 series.

Applications and users

ISO 13347-2 is used by:

• Acoustic test laboratories performing standardized fan noise assessments.
• Fan manufacturers for product development, performance comparisons and demonstrating compliance with sound emission limits.
• Acoustic and mechanical engineers for noise prediction in ducted systems, scaling noise across sizes/speeds, and designing quieter equipment.
• Specifiers and regulatory bodies who require standardized, repeatable sound power data for procurement or compliance.

Practical uses include comparing fans of similar or different types, determining compliance with noise limits, supporting sound predictions in installations, and informing noise‑control engineering.

Related standards

• ISO 13347-1 (general overview)
• ISO 5136 (in‑duct method)
• ISO 10302 (small fans)
• ISO 5801 (fan performance airways)
• ISO 3741 / ISO 3743 series (reverberation room methods)
• ISO 7235 (ducted silencers testing)
  (Also see ISO 13349, ISO 13350 and IEC standards for small domestic fans.)

Keywords: ISO 13347-2, reverberant room method, industrial fans, fan sound power levels, acoustic testing, reference sound source, laboratory measurement, sound power measurement.