SII—Speech intelligibility index standard: ANSI S3.5 1997

The Speech Intelligibility Index Standard (SII) defines a method for computing a physical measure that is highly correlated with the intelligibility of speech. The SII is calculated from acoustical measurements of speech and noise. In this talk the activities of the Working Group for the Speech Intelligibility Standard will be reviewed including the issues to be resolved, the changes, and the additions under consideration. The general framework of the current standard (ANSI S3.5‐1997) is such that new methodologies for specifying the effective (“equivalent”) speech and noise can be easily incorporated as long as they have been tested and found valid for a well specified set of circumstances. The history of the Speech Intelligibility Index (SII) Standard and its relationship to the Articulation Index (AI) and the Speech Transmission Index(STI) will also reviewed. The general philosophy of Speech Intelligibility Index will also be discussed including the definition and specification of its fundamental variables: dynamic speech and noise spectra, information transmission by different bands, and their biologic/evolutionary compatibility with both the threshold of hearing, and the neural tuning.