Articulation Index (AI)

A measurement, expressed as a number between 0 and 1, of the intelligibility of transmitted or processed speech or speech fragments, taking into account the signal-to-noise ratio in each of twenty speech bands.

Below 0.1, speech is considered unintelligible; above 0.6 intelligibility is acceptably high. The masking of onset transients by reverberation reduces the AI by at least 0.1 for each second of reverberation time.

Compare: Speech Communication Criterion, Speech Interference Level.