Sonority hierarchy

Manners of articulation
Obstruent
Plosive (occlusive)
Affricate
Fricative
Sibilant
Sonorant
Nasal
Flap/Tap
Approximant
Liquid
Vowel
Semivowel
Lateral
Trill
Airstreams
Pulmonic
Ejective
Implosive
Lingual (clicks)
Linguo-pulmonic
Linguo-ejective
Alliteration
Assonance
Consonance
See also: Place of articulation
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A sonority hierarchy or sonority scale is a ranking of speech sounds (or phones) by amplitude. For example, if you say the vowel [a], you will produce a much louder sound than if you say the plosive [t]. Sonority hierarchies are especially important when analyzing syllable structure; rules about what segments may appear in onsets or codas together, such as SSP, are formulated in terms of the difference of their sonority values. Some languages also have assimilation rules based on sonority hierarchy, for example, the Finnish potential mood, in which a less sonorous segment changes to copy a more sonorous adjacent segment (e.g. -tne- → -nne-).

Sonority hierarchy

Sonority hierarchies vary somewhat in which sounds are grouped together. The one below is fairly typical:

	vowels	approximants (glides and liquids)	nasals	fricatives	affricates	plosives
syllabic:	+	-
approximant:	+		-
sonorant:	+			-
continuant:	+				-
delayed release:	+					-

Sound types are the most sonorous on the left side of the scale, and become progressively less sonorous towards the right (i.e., fricatives are less sonorous than nasals).

The labels on the left refer to distinctive features, and categories of sounds can be grouped together according to whether they share a feature. For instance, as shown in the sonority hierarchy above, vowels are considered [+syllabic], whereas all consonants (including plosives, affricates, fricatives, etc.) are all considered [-syllabic]. All sound categories falling under [+sonorant] are sonorants, whereas those falling under [-sonorant] are obstruents. In this way, any contiguous set of sound types may be grouped together on the basis of no more than two features (for instance, glides, liquids, and nasals are [-syllabic, +sonorant]).

Sonority scale

In English, the sonority scale, from highest to lowest, is the following:

([a] > [e o] > [i u] > [r] > [l] > [m n] > [z v ð] > [s f θ] > [b d ɡ] > [p t k])

More finely nuanced hierarchies often exist within classes whose members cannot be said to be distinguished by relative sonority. In North American English, for example, of the set /p t k/, /t/ is by far the most subject to weakening when before an unstressed vowel (v. the usual American pronunciation of /t/ as a flap in later, but normally no weakening of /p/ in caper or of /k/ in faker).

In Portuguese, intervocalic /n/ and /l/ are typically lost historically (e.g. Lat. LUNA > /lua/ 'moon', DONARE > /doar/ 'donate', COLORE > /kor/ 'color'), but /r/ remains (CERA > /sera/ 'wax'), whereas Romanian transformed the intervocalic non-geminate /l/ into /r/ (SOLEM > /so̯are/ 'sun') and reduced the geminate /ll/ to /l/ (OLLA > /o̯alə/ 'pot'), but kept unchanged /n/ (LUNA > /lunə/ 'moon') and /r/ (PIRA > /parə/ 'pear'). Similarly, Romance languages often show geminate /mm/ to be weaker than /nn/, and Romance geminate /rr/ is often stronger than other geminates, including /pp tt kk/. In such cases, many phonologists refer not to sonority, but to a more abstract notion of relative strength, which, while once posited as universal in its arrangement, is now known to be language-specific.

External links

• What is the sonority scale?
• Lingua::Phonology::Syllable — Perl module for extracting sonority scale from text.