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Common Intelligibility Scale ("CIS")

Common Intelligibility Scale ("CIS")

The Common Intelligibility Scale (CIS) is a standardised method for measuring and evaluating speech intelligibility in various environments, ensuring effective communication in critical systems.

Derived from objective acoustic measurements and predictive modelling, CIS accounts for factors such as signal-to-noise ratio, reverberation, and distortion.

It uses a standardised scale ranging from 0 (no intelligibility) to 1 (perfect intelligibility) and is widely applied in assessing the performance of public address systems, emergency warning systems, building occupant warning systems, and other communication systems, particularly in emergency scenarios, to help ensure clear, reliable and effective communication.

The Common Intelligibility Scale (CIS) is not directly measured as a standalone metric; rather, it is derived from other speech intelligibility measures such as the Speech Transmission Index (STI) or Articulation Index (AI). These metrics are based on detailed acoustic evaluations of communication systems, and the CIS is calculated as a transformation of their scores to a standardised scale ranging from 0 to 1.

CIS is a derived metric rather than a directly measured one. Its calculation depends on the specific test method and the conditions under which the intelligibility is assessed. Tools like speech analysers and simulation software are often used to conduct these evaluations in controlled or real-world scenarios.

    Disclaimer

    In preparing this definition, we have drawn from various sources including Legislation, Codes, Standards and industry information, research and knowledge.  Like the english language, these definitions may subtly change from time to time. As such these definitions are provided solely on the basis that users will be responsible for making their own assessment of the definition and and are advised to verify all relevant representations, statements and information.