Overview
EN ISO 9053-2:2020 - Acoustics: Determination of airflow resistance (Part 2: Alternating airflow method) specifies an alternating airflow method for measuring the airflow resistance of porous materials used in acoustical applications. Published by CEN/ISO in 2020, this part complements ISO 9053‑1 (static flow method) and provides the test principle, required equipment, specimen preparation rules, measurement procedure, uncertainty estimation and reporting requirements.
Key topics and requirements
- Scope and purpose: Measurement of airflow resistance (R), expressed as the ratio of RMS pressure difference across a specimen to RMS volumetric flow (Δp / q), for porous acoustical materials.
- Definitions and symbols: Clear definitions for airflow resistance, specific airflow resistance (Rs), airflow resistivity (σ), airflow velocity, sound pressure level and related quantities; reference sound pressure is 20 μPa.
- Principle: Uses an alternating (oscillatory) airflow generated by a piston or similar device; the method records RMS pressure and volumetric flow in a measurement cell to obtain R.
- Equipment requirements:
- Device producing alternating airflow (piston or equivalent)
- Sound measuring device and pressure sensors
- Measurement cell / vessel and airtight termination
- Devices to measure static pressure and piston frequency
- Test specimens: Guidance on homogeneity, shape, lateral dimensions and thickness; number of specimens to be tested.
- Procedure and corrections: Step‑by‑step test procedure, thermal conduction correction and acoustic modelling considerations to ensure accurate results.
- Uncertainty and reporting: Annexes provide calculation of measurement uncertainty (GUM guidance), and required content for test reports.
- Informative annexes: Effective ratio of specific heats for air, acoustic flow models, uncertainty calculation examples, and treatment of airflow resistance with perforated supports.
Applications and practical value
- Characterizing porous absorbers, insulation, and acoustic liners for product development and quality control.
- Specifying material input parameters for acoustic modelling, room acoustics design and sound-absorbing product selection.
- Verifying compliance with acoustic performance claims in manufacturing and certification.
- Useful in R&D, test laboratories, façade and building acoustics, HVAC silencer design and automotive/transport acoustic component testing.
Who should use this standard
- Acoustical engineers and consultants
- Materials and insulation manufacturers
- Accredited test laboratories and metrology institutes
- Product certification bodies and building acoustics specialists
- R&D teams developing sound-absorbing materials
Related standards
- ISO 9053‑1 - Determination of airflow resistance by static flow (complements Part 2)
- ISO/IEC Guide 98‑3 (GUM) - Guide for expression of measurement uncertainty
Keywords: EN ISO 9053-2:2020, alternating airflow method, airflow resistance, airflow resistivity, acoustics, porous materials, specific airflow resistance, ISO 9053.
