Overview
ISO/TS 20065:2022 - Acoustics: Objective method for assessing the audibility of tones in noise (Engineering method) defines an objective, engineering procedure for determining when tonal components in environmental noise are audible. It is intended to augment aural impression-based evaluation, especially when subjective judgements disagree. The method applies for tones at frequencies >= 50 Hz (the procedure has not been validated below 50 Hz) and can be implemented in automated, continuous measurement stations.
Key topics and technical requirements
- Objective audibility metric (ΔL): Audibility is defined as the difference between the identified tone level and the masking threshold. The standard specifies how to determine the tone level, masking threshold and resulting audibility.
- Critical band analysis: Uses critical-band concepts to integrate narrow-band levels and derive the critical band level (LG) and mean narrow‑band level (LS) for masking assessment.
- Tone detection and prominence: Procedures to identify prominent tones, compute tone level (LT), and evaluate distinctness and audibility within a critical band.
- Masking index and masking threshold: Methods to calculate the masking threshold and the masking index (av′ ) that quantify tone detectability.
- Measurement procedure and instrumentation: Guidance on sampling, time-windowing, DFT/line spectrum analysis, antialiasing, block length and line spacing (document references recommended ranges for line spacing). References normative requirements to ISO 1996-1 and IEC 61672-1.
- Uncertainty and reporting: Procedures to calculate uncertainty of audibility (ΔL) and recommendations for presenting measurement results, acoustic environment, instruments and data.
- Annexes and implementation aids: Informative annexes cover window/picket-fence effects, ear resolving power, masking explanation, iterative determination methods and worked examples (including supporting example files referenced in the specification).
Applications
- Objective assessment of tonal components in environmental noise monitoring (urban, industrial, transport).
- Dispute resolution when different observers disagree on perceived tonal annoyance.
- Automated analysis in continuous noise monitoring stations and environmental compliance systems.
- Engineering evaluation for noise control design, mitigation planning and impact assessments.
- Specialist analyses such as wind turbine tonal assessment (examples and round‑robin material are referenced in the specification).
Who should use this standard
- Acoustic consultants and noise engineers
- Environmental regulators and compliance officers
- Monitoring station operators and instrumentation/software developers
- Urban planners and industrial facility designers concerned with tonal noise
Related standards
- ISO 1996-1 (environmental noise description, measurement and assessment basics)
- IEC 61672-1 (sound level meter specifications)
Keywords: ISO/TS 20065:2022, audibility of tones in noise, objective method, acoustics, critical band, masking threshold, environmental noise monitoring, continuous measurement stations.