ISO 13347-3:2026

Overview

ISO 13347-3:2026 is an international standard published by the International Organization for Standardization (ISO) that specifies laboratory methods for determining the sound power levels of fans, using enveloping surface techniques. This standard offers an objective, reproducible method for measuring the airborne noise output from fans under strictly controlled test conditions. It applies to a broad range of fan types as defined in ISO 13349-1, covering fans of all sizes-restricted only by practical considerations of test facility size and capacity-and is fundamental for accurate fan noise assessment in compliance with ISO requirements.

The enveloping surface methods outlined in ISO 13347-3:2026 are designed exclusively for laboratory settings, not for in-situ or field noise measurements. The procedures accommodate standardized installation categories for fans and can also provide estimated measurements for ducted fans that are not easily tested using in-duct methods.

Key Topics

• Standardized Measurement of Fan Sound Power
  The standard defines procedures for measuring the sound power level emitted by fans using microphone arrays located on enveloping geometric surfaces (rectangular, spherical, or hemispherical shapes). This involves careful control of background noise, environmental corrections, and test arrangements that reflect how fans are typically installed and operated.

• Applicability and Limitations
  ISO 13347-3:2026 is applicable only for airborne sound emissions and does not assess vibration or the impact of vibration on airborne sound. Small fans may be tested following this document or ISO 10302-1, according to specific use cases.

• Standardized Installation Categories
  The document identifies five installation categories, covering various combinations of free or ducted inlet and outlet arrangements. It specifies how the fan should be mounted for each category to ensure consistent, comparable results.

• Enveloping Surface Methods
  The enveloping surface technique employs hypothetical surfaces surrounding the fan (with or without a reflecting plane), over which sound pressure levels are measured and used to calculate the total sound power output of the fan.

• Uncertainty and Environmental Corrections
  The standard addresses uncertainties in measurement and provides guidance on applying corrections for environmental effects, such as room acoustics and end reflections in test setups.

Applications

ISO 13347-3:2026 is widely used by manufacturers, laboratories, and engineers involved in:

• Product Development and Quality Control:
  Ensuring fans comply with international noise emission requirements and supporting sound optimization during design.
• Performance Certification:
  Providing noise performance data for regulatory or commercial product certification.
• Market Comparison:
  Enabling objective comparison of noise emissions between different fan models and manufacturers.
• Noise Control Engineering:
  Supplying accurate data for environmental noise assessments and facility noise control planning.
• Research and Development:
  Supporting the scientific study and technological improvement of fan acoustic performance.
• Estimation for Ducted Fans:
  Facilitating indirect estimates of ducted sound power when direct in-duct testing is impractical.

Related Standards

• ISO 13347-1:2025 – General overview for determining fan sound power levels under standardized laboratory conditions.
• ISO 3744 – Acoustics: Engineering method for determining sound power levels of noise sources using sound pressure.
• ISO 5801 – Fans: Performance testing using standardized airways.
• ISO 10302-1 – Measurement of airborne noise and structure-borne vibration in small air-moving devices.
• ISO 5136 – In-duct methods for sound power determination in fans and air-moving devices.
• ISO 13349-1 – Fans: Vocabulary and category definitions.
• ISO 13350 – Performance testing for jet fans.

ISO 13347-3:2026 is a key reference for anyone seeking standardized, accurate, and repeatable measurements of fan sound power levels in laboratory environments. Its application promotes consistency, accuracy, and reliability in fan acoustics data, supporting both regulatory compliance and industry best practice.