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:
| STI Value | Quality according to IEC 60268-16 | Intelligibility of Syllables in % | Intelligibility of Words in % | Intelligibility of Sentences in % |
|---|---|---|---|---|
| 0 - 0.3 | bad | 0 - 34 | 0 - 67 | 0 - 89 |
| 0.3 - 0.45 | poor | 34 - 48 | 67 - 78 | 89 - 92 |
| 0.45 - 0.6 | fair | 48 - 67 | 78 - 87 | 92 - 95 |
| 0.6 - 0.75 | good | 67 - 90 | 87 - 94 | 95 - 96 |
| 0.75 - 1 | excellent | 90 - 96 | 94 - 96 | 96 - 100 |
If non-native speakers, people with speech disorders or hard-of-hearing people are involved, other probabilities hold.
It is interesting but not astonishing that STI prediction is independent of the language spoken - not astonishing, as the ability of the channel to transport patterns of physical speech is measured.
Another method is defined 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, or SII.
Read more about this topic: Speech Transmission Index
Famous quotes containing the word scale:
“It is in vain that we would circumscribe the power of one half of our race, and that half by far the most important and influential. If they exert it not for good, they will for evil; if they advance not knowledge, they will perpetuate ignorance. Let women stand where they may in the scale of improvement, their position decides that of the race.”
—Frances Wright (1795–1852)
“‘Tis very certain that each man carries in his eye the exact indication of his rank in the immense scale of men, and we are always learning to read it. A complete man should need no auxiliaries to his personal presence.”
—Ralph Waldo Emerson (1803–1882)
“With a defeated joy,
With an auspicious, and a dropping eye,
With mirth in funeral, and with dirge in marriage,
In equal scale weighing delight and dole.”
—William Shakespeare (1564–1616)