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Canadian raising names a pronunciation pattern in which the starting portion of the diphthongs conventionally transcribed /aɪ/ and /aʊ/ is raised in particular contexts, especially before a voiceless syllable coda. The pattern is associated with Canadian English, while related effects also occur in other North American varieties.^[ref]

Comparing lout and loud in controlled contexts can illustrate a voiceless-versus-voiced following consonant, but an acoustic test should compare repeated tokens and their formant trajectories. Sky Onosson's dissertation separates changes in trajectory from the shortening of vowels before voiceless consonants; its abstract reports different cross-dialect patterns for the two diphthongs. A single midpoint or duration can therefore miss part of the phenomenon. Raising refers to vowel quality, not simply to a higher voice fundamental frequency.

A diphthong is a vowel whose quality changes during its production, conventionally treated as one dynamic vowel unit. A monophthong has relatively stable quality instead. The vowel in English toy, often transcribed [ɔɪ], moves from a back rounded quality toward a high front unrounded quality.^[ref]

A recording can represent that change through formant trajectories. For an invented illustration, let normalized vowel time be $0\le u\le 1$ and setin hertz. These are stipulated linear interpolation tracks, not measurements of toy. Their endpoints differ even if fundamental frequency stays fixed, separating changing vowel quality from voice pitch. Real trajectories need not be linear, and identifying a single diphthong rather than a sequence of separate vowels requires phonological evidence as well as an acoustic curve.

A monophthong is a vowel with relatively stable quality through its central portion, in contrast with a diphthong's substantial movement between qualities. Relatively stable does not mean physically unchanging: neighboring sounds, vocal tract movement and the analysis interval can all affect a recording.^[ref]

For a stipulated acoustic illustration, hold the first two formants at $F_1=300$ and $F_2=2200$ hertz, while varying fundamental frequency from 100 to 150 hertz. The model changes voice pitch without requiring the same change in the formant pattern. Conversely, changing formants can change vowel quality while fundamental frequency stays fixed.

An experimental analysis can record a sustained vowel and compare several points within a consistently chosen interval. Changes concentrated near consonant boundaries need not make the whole segment a diphthong. The distinction therefore combines a phonetic trajectory with an analysis of the language's sound units.

Sky Onosson is a linguist whose research connects phonetics, phonology and quantitative analysis of language variation. His research statement emphasizes the changing acoustic structure of vowels, including diphthongs, and the use of the R for modeling and visualization.^[ref]

His 2018 dissertation investigated Canadian raising by comparing vowel duration and formant trajectories across Canadian and two American dialect groups.^[ref] Comparing a trajectory instead of only one instant helps distinguish a vowel's changing quality from the effects of duration. His work consequently treats time alignment as part of the scientific analysis, rather than assuming that measurements at a single relative time capture every contrast.

Homepage: onosson.github.io/