STI

Speech Transmission Index. Special measurement method and measurement equipment for the objective determination of speech intelligibility in a room. In a good room, the STI value ought to be greater than 0.6 (on a scale of 0 - 1). Practical (reduced) versions that can be implemented in handheld measurement devices are RaSTI (Rapid Speech Transmission Index) and STIPA (Speech Transmission Index, PA systems).