Intelligibility
Encyclopedia
In phonetics
, Intelligibility is a measure of how comprehendible speech is, or the degree to which speech can be understood. Intelligibility is affected by spoken clarity, explicitness, lucidity, comprehensibility, perspicuity, and precision.
Word articulation remains high even when only 1–2% of the wave is unaffected by distortion:
automatically changes speech made in noise through a process called the Lombard effect
. Such speech has increased intelligibility compared to normal speech. It is not only louder but the frequencies of its phonetic fundamental are increased and the durations of its vowels are prolonged. People also tend to make more noticeable facial movements.
is less intelligible than Lombard speech because increased vocal energy produces decreased phonetic information.
. It is characterized by a slower speaking rate, more and longer pauses, elevated speech intensity, increased word duration, "targeted" vowel formants, increased consonant intensity compared to adjacent vowels, and a number of phonological changes (including fewer reduced vowels and more released stop bursts).
—uses a simplified syntax
and a small and easier-to-understand vocabulary
than speech directed to adults Compared to adult directed speech, it has a higher fundamental frequency, exaggerated pitch range, and slower rate.
Phonetics
Phonetics is a branch of linguistics that comprises the study of the sounds of human speech, or—in the case of sign languages—the equivalent aspects of sign. It is concerned with the physical properties of speech sounds or signs : their physiological production, acoustic properties, auditory...
, Intelligibility is a measure of how comprehendible speech is, or the degree to which speech can be understood. Intelligibility is affected by spoken clarity, explicitness, lucidity, comprehensibility, perspicuity, and precision.
Noise levels
For satisfactory communication, the average speech level should exceed that of an interfering noise by 6dB; lower sound:noise ratios are rarely acceptable (Moore, 1997). Manifesting in a wide frequency range, speech is quite resistant to many types of masking frequency cut-off—Moore reports, for example, that a band of frequencies from 1000 Hz to 2000 Hz is sufficient (sentence articulation score of about 90%).| Quantity to be measured | Unit of measurement | Good values |
|---|---|---|
| STI Speech Transmission Index Speech Transmission Index, short STI is a measure of speech transmission quality. The absolute measurement of speech intelligibility is a complex science. The STI measures some physical characteristics of a transmission channel , and expresses the ability of the channel to carry across the... |
Intelligibility (international known) | > 0.6 |
| CIS | Intelligibility (international known) | > 0.78 |
| %Alcons Alcons Alcons means Percentage Articulation Loss of Consonants = %ALcons. This machine measure of intelligibility is closely associated with the TEF sound analyzer. It is computed from measurements of the Direct-to-Reverberant Ratio and the Early Decay Time using a set of correlations defined by... |
Articulation loss (popular in USA) | < 10 % |
| C50 | Clarity index (widespread in Germany) | > 3 dB |
| RASTI (obsolete) | Intelligibility (international known) | > 0.6 |
Word articulation remains high even when only 1–2% of the wave is unaffected by distortion:
Lombard speech
The human brainHuman brain
The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...
automatically changes speech made in noise through a process called the Lombard effect
Lombard effect
thumb|250 px|[[Great tit]]s sing at a higher frequency in [[noise pollution|noise polluted]] urban surroundings than quieter ones to help overcome the [[auditory masking]] that would otherwise impair other birds hearing their [[bird vocalization|song]]...
. Such speech has increased intelligibility compared to normal speech. It is not only louder but the frequencies of its phonetic fundamental are increased and the durations of its vowels are prolonged. People also tend to make more noticeable facial movements.
Screaming
Shouted speechScreaming
A scream, shout, shriek, hoot, holler, vociferation, yell, outcry, or bellow is a loud vocalization in which air is passed through the vocal folds with greater force than is used in regular or close-distance vocalization...
is less intelligible than Lombard speech because increased vocal energy produces decreased phonetic information.
Clear speech
Clear speech is used when talking to a person with a hearing impairmentHearing impairment
-Definition:Deafness is the inability for the ear to interpret certain or all frequencies of sound.-Environmental Situations:Deafness can be caused by environmental situations such as noise, trauma, or other ear defections...
. It is characterized by a slower speaking rate, more and longer pauses, elevated speech intensity, increased word duration, "targeted" vowel formants, increased consonant intensity compared to adjacent vowels, and a number of phonological changes (including fewer reduced vowels and more released stop bursts).
Infant-directed speech
Infant-directed speech—or Baby talkBaby talk
Baby talk, also referred to as caretaker speech, infant-directed speech or child-directed speech and informally as "motherese", "parentese", "mommy talk", or "daddy talk" is a nonstandard form of speech used by adults in talking to toddlers and infants.It is usually delivered with a "cooing"...
—uses a simplified syntax
Syntax
In linguistics, syntax is the study of the principles and rules for constructing phrases and sentences in natural languages....
and a small and easier-to-understand vocabulary
Vocabulary
A person's vocabulary is the set of words within a language that are familiar to that person. A vocabulary usually develops with age, and serves as a useful and fundamental tool for communication and acquiring knowledge...
than speech directed to adults Compared to adult directed speech, it has a higher fundamental frequency, exaggerated pitch range, and slower rate.