featuring electro-acoustic components (such as loudspeakers and microphones) became fairly common, and led to complaints about inaccurate results. The use of RASTI was even specified by some application standards (such as CAA specification 15 for aircraft cabin PA systems) for applications featuring electro-acoustics, simply because it was the only feasible method at the time. The inadequacies of RASTI were sometimes simply accepted for lack of a better alternative. TNO did produce and sell instruments for measuring full STI and various other STI derivatives, but these devices were relatively expensive, large and heavy. Around the year 2000, the need for an alternative to RASTI that could also be applied safely to Public Address (PA) systems had become fully apparent. At TNO, Jan Verhave and Herman Steeneken started work on a new STI method, that would later become known as STIPA (STI for Public Address systems). The first device to include STIPA measurements available for sale to the general public was made by Gold-Line. At this time, STIPA measuring instruments are available from various manufacturers. RASTI was standardized internationally in 1988, in IEC-60268-16. Since then, IEC-60268-16 has been revised three times, the latest revisions (rev.4) appearing in 2011. Each revision included updates of the STI methodology that had become accepted in the STI research community over time, such as the inclusion of redundancy between adjacent octave bands (rev.2), level-dependent auditory masking (rev.3) and various methods for applying the STI to specific populations such as non-natives and the hearing impaired (rev.4). An IEC maintenance team is currently working on rev. 5. RASTI was declared obsolete by the IEC in June 2011, with the appearance of rev. 4 of IEC-602682-16. At this time, this simplified STI derivative was still stipulated as a standard method in some industries. STIPA is now seen as the successor to RASTI for almost every application. Scale STI is a numeric representation measure of communication channel characteristics whose value varies from 0 = bad to 1 = excellent. On this scale, an STI of at least .5 is desirable for most applications. Barnett (1995, 1999) proposed to use a reference scale, the Common Intelligibility Scale (CIS), based on a mathematical relation with STI (CIS = 1 + log (STI)). STI predicts the likelihood of syllables, words and sentences being comprehended. As an example, for native speakers, this likelihood is given by: If non-native speakers, people with speech disorders or hard-of-hearing