Historical
ANSI/ASA S3.5-1997 (R2017)
Methods for Calculation of the Speech Intelligibility Index
Defines a method for computing a physical measure that is highly correlated with the intelligibility of speech as evaluated by speech perception tests given a group of talkers and listeners. This measure is called the speech Intelligibility Index, SII. The SII is calculated from acoustical measurements of speech and noise.
Acoustical Society of America [asa]