Speech intelligibility is measured by reproducing a known signal (the STIPA test signal) and measuring the quality of that signal as it reaches each of the measurement positions. Measurement units are STI (Speech Transmission Index) or CIS (Common Intelligibility Scale).
What is common intelligibility scale?
Common Intelligibility Scale (CIS), a method for ranking articulation based on a mathematical relation with STI : speech transmission index, where (CIS = 1 + log (STI)). Instantaneous Speech Power Definition (IEC 801-29-410) rate at which sound energy is being radiated by a speech source at any given instant.
How is Stipa calculated?
AudioTools STIPA calculates the auditory masking factor for each of the octave bands using the formulas in section A. 3.2 of IEC 60268-16:2011 and multiples the calculated TI by this corrected factor. The final determination of the STI is completed by taking a weighted average of each octave band's adjusted TI.
What is rapid speech transmission index?
You recall that RASTI stands for RApid Speech Transmission Index. It is basically a short form of the STI intended as a means to quickly estimate speech intelligibility. The speed comes from analyzing only 2 octave bands (500 Hz and 2 kHz) instead of the 7 in the STI.
How do you calculate STI?
Technically, the STI is calculated as the weighted sum of modulation transfer indices MTI, one for each octave frequency band from 125 Hz through 8 kHz (where each MTI value is derived from MTF values over 14 different modulation frequencies, see Table 2) taking into account auditory effects according to IEC 60268-16.
What is the measurement standard for speech intelligibility?
Speech Intelligibility is the measure of how accurately people understand a spoken message. The XL2 measures the speech intelligibility according to the standard IEC 60268-16:2020 (edition 5). STI and STIPA are the most established methods for measuring speech intelligibility.
What is intelligibility rating scale?
The overall intelligibility of speech is rated on a five-point scale to specify how well the speaker can make his or herself understood when reading the Rainbow Passage aloud. Speech is very difficult to understand-only isolated words or phrases are intelligible.
What is STI value?
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.