ToBI (; an abbreviation of tones and break indices) is a set of conventions for transcribing and annotating the prosody of speech. The term "ToBI" is sometimes used to refer to the conventions used for describing American English specifically,[1] which was the first ToBI system, developed by Mary Beckman and Janet Pierrehumbert, among others.[2] Other ToBI systems have been defined for a number of languages; for example, J-ToBI refers to the ToBI conventions for Tokyo Japanese,[3] and an adaptation of ToBI to describe Dutch intonation was developed by Carlos Gussenhoven, and called ToDI.[4] Another variation of ToBI, called IViE (Intonational Variation in English), was established in 1998 to enable comparison between several dialects of British English.[5]
A full ToBI transcription consists of six parts: (a) an audio recording, (b) an electronic print-out or paper record of the F0 (fundamental pitch), (c) a tones tier, with an analysis of the tonal events in terms of H and L, (d) a words tier with the words of the utterance in ordinary writing, (e) a break-index tier showing the strength of the junctures, and (f) a miscellaneous tier with comments.[6]
Tonal events include pitch accents, phrase accents, and boundary tones.
Pitch accents, written as H* or L* (high and low tones, respectively), are typically realized on words that carry the most information in a sentence. For example, in the sentence "Mary went to the store to get some milk", a natural pronunciation would include pitch accents on "Mary", "store", and "milk". Other kinds of pitch accents include L*+H (a syllable which starts with a low accent and then rises) and L+H* (again low-high on one syllable, but with the second part accented).[7]
Phrase accents, written H- or L-, are the tones between a pitch accent and a boundary tone. For example, the intonation at the end of a question might be H*L-H%, indicating that the pitch starts high, falls to a low, and rises again; or L*H-H%, indicating that the pitch starts low, then rises steadily to a high.
Boundary tones, written with H% and L%, are affiliated not to words but to phrase edges. For example, the sentence "Mary went to the store" can be pronounced as a statement or a question ("Mary went to the store." vs. "Mary went to the store?"). The contrast between the statement and the question is signalled by a boundary tone at the end of the phrase: a low boundary tone causes a falling pitch contour, signalling the statement, whereas a high boundary tone causes a rising pitch contour, signalling the question.
Break indices are numbers indicating how strong the break is between words:
The English ToBI standard distinguishes four or five levels of boundary strength, corresponding roughly to breaks between constituents at different levels of the Prosodic Hierarchy.[8] [9] One signal of boundary strength is lengthening of the preceding syllable: the stronger the boundary, the more lengthening of the preceding syllable.[10] In some versions, level 2 is omitted.