IEC 60268-16:2020

Overview

IEC 60268-16:2020 is an international standard developed by the International Electrotechnical Commission (IEC) focused on sound system equipment and specifically on the objective rating of speech intelligibility using the Speech Transmission Index (STI). This comprehensive document defines the STI model, test signals, and both measurement and prediction methods that are essential for assessing speech intelligibility in various audio and communication environments. The 2020 edition is a significant technical revision that replaces the earlier 2011 edition, incorporating updates such as refined test signals, measurement corrections, and expanded guidance on prediction procedures and device verification.

The primary goal of IEC 60268-16:2020 is to provide all users-including professionals in audio engineering, communications, and acoustics-with a practical manual for implementing the STI model accurately. While it does not set certification criteria for specific transmission channels like voice-alarm systems, it includes typical application values to aid implementation.

Key Topics

• STI Model and Theory: The standard explains the theoretical framework of the STI, including modulation transfer functions and the impact of frequency bands on speech intelligibility.
• Test Signals: Defines male speech test signals with updated frequency spectra and standardized test signals used to simulate speech for measurement.
• Measurement Methods: Distinguishes between direct and indirect STI measurement techniques, detailing user guidance, applications, and limitations of each.
• Limitations: Addresses challenges such as fluctuating noise, echo effects, digital voice compression, nonlinear distortions, and frequency shifts that can affect STI accuracy.
• Device Verification: Introduces procedures for verifying the performance of STI measuring instruments to ensure reliable results.
• Post-Processing and Interpretation: Provides extensive guidelines on analyzing measured data, including spatial averaging and adjustment for varying ambient noise and speech levels.
• Prediction Tools: Describes the use of STI in design predictions through statistical and simulated impulse response methods.
• Annexes for Practical Use: Includes informative annexes elaborating on the STI concept basis, detailed measurement procedures, device verification protocols, and user guidance for practical test scenarios.

Applications

IEC 60268-16:2020 is widely applicable in fields requiring objective evaluation and enhancement of speech intelligibility within audio and communication systems. Key applications include:

• Public Address (PA) Systems: Ensuring speech announcements are clearly intelligible in large venues, transport hubs, and emergency systems.
• Telecommunication Systems: Assessing clarity and intelligibility in wired, wireless, and VoIP communication.
• Voice Alarm Systems: Supporting design and testing to improve voice message audibility during emergencies.
• Acoustic Design and Audio Engineering: Optimizing room acoustics and sound system configurations to achieve clear speech transmission.
• Hearing-Impaired Friendly Environments: Evaluating speech transmission in facilities to accommodate hearing-impaired listeners by understanding STI limitations.
• Research and Development: Providing standardized methods for developing new audio technologies and intelligibility measurement tools.

Related Standards

Professionals using IEC 60268-16:2020 should consider related standards for comprehensive system assessment and integration:

• IEC 60268 Series: Additional parts in this series cover general audio equipment requirements, electroacoustic devices, and loudspeaker standards.
• ISO 9921: Covers the assessment of speech communication performance and intelligibility in noisy environments.
• ITU-T P.563: Provides objective speech quality measurement techniques relevant for telecommunication systems.
• IEC 60601: For audiometric evaluations related to hearing thresholds which may relate to intelligibility assessments.
• ISO 3382: Addresses room acoustic measurement techniques including impulse response methods used for STI indirect measurement.

By following the IEC 60268-16:2020 standards, audio and communication system designers, engineers, and acousticians can systematically assess and enhance speech intelligibility, ensuring clearer communication in diverse environments. This contributes to higher safety, user satisfaction, and system performance.