Overview
ISO 5114-1:2024 - "Acoustics - Determination of uncertainties associated with sound emission measures - Part 1: Sound power levels determined from sound pressure measurements" - provides guidance for estimating measurement uncertainty of sound power levels derived from sound pressure measurements. It applies to measurements performed under ISO test methods such as ISO 3741, ISO 3743-1, ISO 3743-2, ISO 3744, ISO 3745, ISO 3746 and ISO 3747, or noise test codes based on those standards. The document defines a clear concept for reporting uncertainty in decibels, consistent with the ISO/IEC Guide 98-3 approach to uncertainty evaluation.
Key technical topics and requirements
- Uncertainty model and terminology: Defines measurement result, measurement uncertainty, expanded uncertainty, coverage factor, repeatability and reproducibility conditions.
- Decomposition of total uncertainty: Introduces the total standard deviation σ_tot as the combination of:
- σ_R0 - standard deviation of reproducibility of the method (variation across labs, instruments, procedures); and
- σ_omc - standard deviation due to operating and mounting conditions (instability of the source under test).
- Relationship: σ_tot = sqrt(σ_R0^2 + σ_omc^2).
- Expanded uncertainty: Expanded measurement uncertainty UL is calculated as UL = k · σ_tot, where the coverage factor k is chosen according to the desired confidence level (e.g., k = 2 for ~95% two-sided confidence).
- Determination methods:
- Round robin tests to derive σ_R0 for a machine family or measurement procedure.
- Mathematical modelling / detailed uncertainty budgets to derive component contributions.
- Practical measurement guidance:
- Procedures for repeated measurements to evaluate σ_omc (repeating mounting and operating conditions, background noise correction).
- Recommendations for defining representative operating and mounting conditions in noise test codes and test reports.
- Annexes: Informative detailed uncertainty budgets for common measurement situations - approximated free-field (direct enveloping), diffuse-field, and use of reference sound sources.
Practical applications and who uses this standard
- Acoustical testing laboratories use ISO 5114-1 to quantify and report uncertainties with sound power measurements, ensuring reliable comparison and compliance checks.
- Manufacturers and product development teams apply the standard when declaring sound power levels and assessing the effect of mounting or operating variability.
- Regulatory bodies and conformity assessors rely on standardized uncertainty reporting to judge compliance with noise limits.
- Test code writers and standards developers use its guidance to set representative σ values for specific machinery families and to structure noise test codes.
- Acoustical consultants use the uncertainty framework when advising on measurement methods, designing round robin studies, or preparing uncertainty budgets.
Related standards
Keywords: ISO 5114-1, acoustics, measurement uncertainty, sound power level, sound pressure measurements, ISO 3744, reproducibility, σ_R0, σ_omc, expanded uncertainty, uncertainty budget, round robin tests.
Open preview (PDF)Acoustics — Determination of uncertainties associated with sound emission measures — Part 1: Sound power levels determined from sound pressure measurements