Overview
EN ISO 12999-2:2020 - Acoustics: Determination and application of measurement uncertainties in building acoustics - Part 2: Sound absorption (ISO 12999-2:2020) specifies procedures for quantifying and reporting the measurement uncertainty of sound absorption results. It was prepared by ISO/TC 43 with CEN endorsement and gives a pragmatic approach (based on repeatability and reproducibility) to uncertainty evaluation where a full GUM model is impractical.
Key topics and requirements
- Scope of uncertainty calculations
- Uncertainty of sound absorption coefficients and equivalent sound absorption areas measured per ISO 354.
- Uncertainty of practical and weighted sound absorption coefficients per ISO 11654.
- Uncertainty of the object sound absorption coefficient per ISO 20189.
- Uncertainty of single-number ratings per EN 1793‑1.
- Uncertainty approach
- Uses repeatability and reproducibility standard deviations (derived from inter‑laboratory studies) where complete mathematical measurement models are not feasible.
- Provides standard uncertainties (u) and guidance to derive expanded uncertainties (U) with appropriate coverage factors (k).
- Frequency-band treatment
- Uncertainties are specified in one‑third octave bands; the standard includes a formula and frequency-dependent constants (m, n) to calculate reproducibility standard deviations for band-by-band sound absorption coefficients.
- Reporting
- Guidance on how to include uncertainty information when reporting measured or weighted sound absorption coefficients, improving transparency and comparability of test results.
Practical applications
- Ensures consistent, traceable uncertainty reporting for laboratory test reports and product data sheets (e.g., ceiling tiles, absorptive panels, foams).
- Supports acoustic design and simulation by providing realistic bounds on measured absorption used in room acoustic models.
- Used in conformity assessment, certification and compliance checks where uncertainty affects pass/fail decisions or performance declarations.
- Helps test laboratories demonstrate measurement capability and supports accreditation (e.g., ISO/IEC 17025) and inter-laboratory comparison work.
Who should use this standard
- Acoustic test laboratories and engineers performing ISO 354 measurements
- Product manufacturers and R&D teams for absorptive materials
- Acoustic consultants, specifiers and building façade/traffic-noise engineers
- Certification bodies, procurement specialists and accreditation assessors
Related standards
- ISO 354 - Measurement of sound absorption in a reverberation room
- ISO 11654 - Rating of sound absorption
- ISO 20189 - Object sound absorption coefficient
- EN 1793‑1 - Road traffic noise: airborne sound insulation and absorption
- ISO/IEC Guide 98-3 (GUM) and ISO 5725 series - uncertainty and inter-lab methods
Keywords: EN ISO 12999-2:2020, sound absorption, measurement uncertainty, building acoustics, ISO 354, ISO 11654, ISO 20189, EN 1793-1, reproducibility, repeatability, one-third octave bands.
