IEC 61265:2018

Overview

IEC 61265:2018 is the international standard developed by the International Electrotechnical Commission (IEC) that specifies the performance requirements for electroacoustic instruments used in the measurement of aircraft noise, particularly for noise certification purposes. This standard ensures that measurement systems used to determine sound pressure levels for aircraft noise certification are consistent, reliable, and accurate, enabling fair comparisons among different aircraft models and ensuring compliance with regulatory requirements.

IEC 61265:2018 applies to complete measuring systems, typically consisting of components such as a microphone (with windscreen and accessories), data recording and processing devices, and output units. The standard covers requirements for these systems to operate optionally on either analog or digital principles. By providing methods for periodic testing and verification of system performance, this standard supports accurate and traceable aircraft noise measurements in both flight and ground conditions.

Key Topics

• Electroacoustic Performance Requirements: Detailed specifications for instrument combinations used in aircraft noise measurement, ensuring consistency across different systems and test environments.
• System Composition: Applicable to whole measurement chains, extending from microphone and accessories to processing and output devices.
• Microphone Configurations: Clarifies requirements for pressure and free-field microphones, as well as specialized configurations like ground plane and grazing incidence arrangements.
• Digital vs. Analog Systems: Updates and clarifications on the requirements for both digital and analog measurement systems, including digital audio recording.
• Weighted and Spectral Measurements: Introduction of performance requirements for weighted measurements (beyond one-third-octave band), relevant for specific aircraft types.
• Measurement Uncertainty: Addition of explicit requirements for evaluating and documenting uncertainty in aircraft noise measurements, supporting regulatory confidence.
• Calibration and Verification: Methods for initial and periodic performance verification, ensuring ongoing conformance of the measurement system to the standard.
• Reference Environmental Conditions: Specifies controlled conditions (temperature, pressure, humidity) for consistent calibration and results.

Applications

The practical value of IEC 61265:2018 lies in its role as the foundation for noise certification of aircraft as required by regulatory bodies such as ICAO and national aviation authorities. Key applications include:

• Aircraft Noise Certification: Instruments compliant with this standard are used for official certification testing of fixed-wing and rotary aircraft according to international regulations.
• Aircraft Comparison: Operators, manufacturers, and authorities use compliant measurement systems to compare aircraft noise performances, assisting in design, procurement, and regulatory decisions.
• Regulatory Compliance: Ensures that noise measurements meet the requirements of ICAO Annex 16 and related local regulations.
• Periodic Performance Verification: Aviation testing laboratories and agencies engage in regular system checks using the verification methods specified, maintaining traceability and credibility in reported noise levels.
• Support for Modern Aircraft Types: The 2018 revision adds guidance for measurements on aircraft types beyond large transport aeroplanes, such as helicopters and lighter planes, expanding the standard's relevance.

Related Standards

For effective implementation of IEC 61265:2018, users should also refer to several related standards in the area of electroacoustic measurement and aircraft noise certification:

• IEC 60942: Electroacoustics - Sound calibrators (requirements for devices used to calibrate microphones and systems)
• IEC 61260-1: Electroacoustics - Octave-band and fractional-octave-band filters - Part 1: Specifications
• IEC 61672-1: Electroacoustics - Sound level meters - Part 1: Specifications
• ICAO Annex 16: Environmental Protection, Volume I - Aircraft Noise (establishes the noise certification requirements referenced by IEC 61265:2018)
• ISO/IEC Directives: Guides for the drafting and application of international standards in electronics and acoustics

Conclusion

IEC 61265:2018 is the internationally recognized reference for organizations seeking reliable, reproducible, and regulatory-compliant measurement of aircraft noise. By adopting systems and procedures in line with this standard, stakeholders across the aviation sector-manufacturers, regulatory authorities, and test laboratories-ensure the accuracy and trustworthiness of aircraft noise certification results, contributing to both environmental protection and industry standardization.