Sibilant

Sibilance is a manner of articulation of fricative and affricate consonants, made by directing a stream of air with the tongue towards the sharp edge of the teeth, which are held close together; a consonant that uses sibilance may be called a sibilant, or a strident. Examples of sibilants are the consonants at the beginning of the English words sip, zip, ship, chip, and jump, and the second consonant in vision. The symbols in the International Phonetic Alphabet used to denote the sibilant sounds in these words are, respectively, [s] [z] [ʃ] [tʃ] [dʒ]. More specifically, the sounds [tʃ] [dʒ], as in chip and jump, are affricates, whereas the rest are fricatives. Sibilants have a characteristically intense sound, which accounts for their non-linguistic use in getting one's attention (e.g. calling someone using "psst!" or quieting someone using "shhhh!").

In the alveolar hissing sibilants [s] and [z], the back of the tongue forms a narrow channel (is grooved) to focus the stream of air more intensely, resulting in a high pitch. With the hushing sibilants (occasionally termed shibilants), such as English [ʃ], [tʃ], [ʒ], and [dʒ], the tongue is flatter, and the resulting pitch lower.

Because all sibilants are also stridents, the terms are sometimes used interchangeably. However, the terms do not mean the same thing. The English stridents are /f, v, s, z, ʃ, ʒ, tʃ, dʒ/. The English sibilants are a more high pitched subset of the stridents. The English sibilants are /s, z, ʃ, ʒ, tʃ, dʒ/. /f/ and /v/ are stridents, but not sibilants, because they are lower in pitch.

"Stridency" refers to the perceptual intensity of the sound of a sibilant consonant, or obstacle fricatives/affricates, which refers to the critical role of the teeth in producing the sound as an obstacle to the airstream. Non-sibilant fricatives and affricates produce their characteristic sound directly with the tongue or lips etc. and the place of contact in the mouth, without secondary involvement of the teeth.

The characteristic intensity of sibilants means that small variations in tongue shape and position are perceivable, with the result that there are a large number of sibilant types that contrast in various languages.

Acoustics

Sibilants are louder than their non-sibilant counterparts, and most of their acoustic energy occurs at higher frequencies than non-sibilant fricatives. [s] has the most acoustic strength at around 8,000 Hz, but can reach as high as 10,000 Hz. [ʃ] has the bulk of its acoustic energy at around 4,000 Hz, but can extend up to around 8,000 Hz.

Sibilant types

All sibilants are coronal consonants (made with the tip or front part of the tongue). However, there is a great deal of variety among sibilants as to tongue shape, point of contact on the tongue, and point of contact on the upper side of the mouth.

The following variables affect sibilant sound quality, and, along with their possible values, are ordered from sharpest (highest-pitched) to dullest (lowest-pitched):

• Tongue shape: grooved, alveolo-palatal, palato-alveolar, retroflex
• Place of articulation (point of contact on the upper side of the mouth): dental or denti-alveolar, alveolar, postalveolar, palatal
• Point of contact on the tongue: laminal "closed" (see below), laminal non-"closed", apical, subapical

Generally, the values of the different variables co-occur so as to produce an overall sharper or duller sound. For example, a laminal denti-alveolar grooved sibilant occurs in Polish, and a subapical palatal retroflex sibilant occurs in Toda.

Tongue shape

The main distinction is the shape of the tongue. Most sibilants have a groove running down the centerline of the tongue that helps focus the airstream, but it's not known how widespread this is. In addition, the following tongue shapes are described, from sharpest and highest-pitched to dullest and lowest-pitched:

• Hollow (e.g. [s z]): This hollow accepts a large volume of air that is forced through a typically narrow aperture that directs a high-velocity jet of air against the teeth, which results in a high-pitched, piercing "hissing" sound. Because of the prominence of these sounds, they are the most common and most stable of sibilants cross-linguistically. They occur in English, where they are denoted with a letter s or z, as in soon or zone.
• Alveolo-palatal (e.g. [ɕ ʑ]): with a convex, V-shaped tongue, and highly palatalized (middle of the tongue strongly raised/bowed).
• Palato-alveolar (e.g. [ʃ ʒ]): with a "domed" tongue (convex and moderately palatalized). These sounds occur in English, where they are denoted with letter combinations such as sh, ch, g, j or si, as in shin, chin, gin and vision.
• Retroflex (e.g. [ʂ ʐ]): with a flat or concave tongue, and no palatalization. These sounds occur in a large number of varieties, some of which also go by other names (e.g. "flat postalveolar" or "apico-alveolar"). The subapical palatal or "true" retroflex sounds are the very dullest and lowest-pitched of all the sibilants.

The latter three post-alveolar types of sounds are often known as "hushing" sounds because of their quality, as opposed to the "hissing" alveolar sounds. The alveolar sounds in fact occur in several varieties, in addition to the normal sound of English s:

• Palatalized: Sibilants can occur with or without raising the tongue body to the palate (palatalization). Palatalized alveolars are transcribed e.g. [sʲ] and occur in Russian; they sound similar to the cluster [sj] occurring in the middle of the English phrase miss you.
• Lisping: Alveolar sibilants made with the tip of the tongue (apical) near the upper teeth have a softer sound reminiscent of (but still sharper-sounding than) the "lisping" [θ] sound of English think. These sounds are relatively uncommon, but occur in some of the indigenous languages of California as well as in the Spanish dialects of eastern Andalusia (southeast Spain), in cities such as Granada, Huelva, Cordoba, Jaén and Almeria. In these dialects, the lisping sibilant [s̺] (sometimes indicated in Spanish dialectology as ⟨s̄⟩) is the normal pronunciation of the letters s and z, as well as c before i or e, replacing the [s] or [θ] that occurs elsewhere in Andalucia.

Speaking non-technically, the retroflex consonant [ʂ] sounds somewhat like a mixture between the regular English [ʃ] of "ship" and a strong American "r"; while the alveolo-palatal consonant [ɕ] sounds somewhat like a mixture of English [ʃ] of "ship" and the [sj] in the middle of "miss you".

Place of articulation

Sibilants can be made at any coronal articulation, i.e. the tongue can contact the upper side of the mouth anywhere from the upper teeth (dental) to the hard palate (palatal), with the in-between articulations being denti-alveolar, alveolar and postalveolar.

Point of contact on the tongue

The tongue can contact the upper side of the mouth with the very tip of the tongue (an apical articulation, e.g. [ʃ̺]); with the surface just behind the tip, called the blade of the tongue (a laminal articulation, e.g. [ʃ̻]); or with the underside of the tip (a subapical articulation). Apical and subapical articulations are always tongue-up, with the tip of the tongue above the teeth, while laminal articulations can be either tongue-up or tongue-down, with the tip of the tongue behind the lower teeth. This distinction is particularly important for retroflex sibilants, because all three varieties can occur, with noticeably different sound qualities. For more information on these variants and their relation to sibilants, see the article on postalveolar consonants.

For tongue-down laminal articulations, an additional distinction can be made depending on where exactly behind the lower teeth the tongue tip is placed. A little ways back from the lower teeth is a hollow area (or pit) in the lower surface of the mouth. When the tongue tip rests in this hollow area, there is an empty space below the tongue (a sublingual cavity), which results in a relatively duller sound. When the tip of the tongue rests against the lower teeth, there is no sublingual cavity, resulting in a sharper sound. Usually, the position of the tip of the tongue correlates with the grooved vs. hushing tongue shape so as to maximize the differences. However, the palato-alveolar sibilants in the Northwest Caucasian languages such as Ubykh are an exception. These sounds have the tongue tip resting directly against the lower teeth, which gives the sounds a quality that Catford describes as "hissing-hushing". Ladefoged and Maddieson term this a "closed laminal postalveolar" articulation, and transcribe them (following Catford) as [ŝ, ẑ], although this is not an IPA notation. See the article on postalveolar consonants for more information.

Symbols in the IPA

The following table shows the types of sibilant fricatives defined in the International Phonetic Alphabet:

IPA signs for sibilants

Voiceless						Voiced
IPA	Description	Example				IPA	Description	Example
		Language	Orthography	IPA	Meaning			Language	Orthography	IPA	Meaning
	voiceless alveolar sibilant	English	sip	[sɪp]	sip		voiced alveolar sibilant	English	zip	[zɪp]	zip
	voiceless alveolo-palatal sibilant	Mandarin	小 (xiǎo)	[ɕiɑu˨˩˦]	small		voiced alveolo-palatal sibilant	Polish	zioło	[ʑɔwɔ]	herb
	voiceless palato-alveolar sibilant	English	shin	[ʃɪn]	shin		voiced palato-alveolar sibilant	English	vision	[vɪʒən]	vision
	voiceless retroflex sibilant	Mandarin	上海 (Shànghǎi)	[ʂɑ̂ŋ.xàɪ]	Shanghai		voiced retroflex sibilant	Russian Polish	жаба żaba	[ʐaba]	toad frog

Diacritics can be used for finer detail. For example, apical and laminal alveolars can be specified as [s̺] vs [s̻]; a dental (or more likely denti-alveolar) sibilant as [s̪]; a palatalized alveolar as [sʲ]; and a generic "retracted sibilant" as [s̠], a transcription frequently used for the sharper-quality types of retroflex consonants (e.g. the laminal "flat" type and the "apico-alveolar" type). There is no diacritic to denote the laminal "closed" articulation of palato-alveolars in the Northwest Caucasian languages, but they are sometimes provisionally transcribed as [ŝ ẑ].

Possible combinations

The attested possibilities, with exemplar languages, are as follows. Note that the IPA diacritics are simplified; some articulations would require two diacritics to be fully specified, but only one is used in order to keep the results legible without the need for OpenType IPA fonts. Also, Ladefoged has resurrected an obsolete IPA symbol, the under dot, to indicate apical postalveolar (normally included in the category of retroflex consonants), and that notation is used here. (Note that the notation s̠, ṣ is sometimes reversed; either may also be called 'retroflex' and written ʂ.)

IPA	Tongue shape	Place of articulation (mouth)	Place of articulation (tongue)	Exemplifying languages
[s̺̪ z̺̪]	hollow	dental	apical	southeast European Spanish s/z, Kumeyaay
[s̪ z̪]		denti-alveolar	laminal	Polish s, z; Basque z, tz
[s̺ z̺]		alveolar	apical	northern peninsular Spanish s; Basque s, ts; Mandarin s, z, c (apical, dental or alveolar)
[s z]			apical or laminal	English s, z (alveolar, laminal or apical); American or southwest European Spanish s/z
[s̻ z̻]			laminal	Toda, Ubykh, Abkhaz
[ʃ ʒ]	domed	postalveolar	apical or laminal	English sh, ch, j, zh and French ch, j ([ʃʷ ʒʷ])
[ʃ̻ ʒ̻]			laminal	Toda; Basque x, tx
[ɕ ʑ]	palatalized			Mandarin x, j, q; Polish ć, ś, ź, dź; Ubykh; Abkhaz
[ŝ ẑ] (ad hoc transcription)	hollow (no cavity)			Ubykh; Abkhaz
[s̱ ẕ], [ʂ̻ ʐ̻]	hollow or flat (cavity under tongue)			Polish sz, rz, cz, dż ([ʂ̻ʷ ʐ̻ʷ]); Mandarin sh, zh, ch
[ʂ ʐ], [ṣ ẓ], etc.	hollow		apical	Ubykh; Abkhaz; Kumeyaay; Toda
[ʂ ʐ]	curled	palatal (or postalveolar?)	subapical	Toda

^1 These sounds are usually just transcribed ⟨ʂ ʐ⟩. Apical postalveolar and subapical palatal sibilants do not contrast in any language, but if necessary, apical postalveolars can be transcribed with an apical diacritic, as ⟨s̠̺ z̠̺⟩ or ⟨ʂ̺ ʐ̺⟩. Ladefoged resurrects the old retroflex sub-dot for apical retroflexes, ⟨ṣ ẓ⟩ Also seen in the literature on e.g. Hindi and Norwegian is ⟨ᶘ ᶚ⟩ – the domed articulation of [ʃ ʒ] precludes a subapical realization.

Whistled sibilants

Whistled sibilants occur in speech pathology and may be caused by dental prostheses or orthodontics. However, they also occur phonemically in several southern Bantu languages, the best known being Shona. These have been variously described—as labialized but not velarized, as retroflex, etc., but none of these articulations are required for the sounds. Using the Extended IPA, Shona sv and zv may be transcribed ⟨s͎⟩ and ⟨z͎⟩. Other transcriptions seen include purely labialized ⟨s̫⟩ and ⟨z̫⟩ (Ladefoged and Maddieson 1996) and labially co-articulated ⟨sᶲ⟩ and ⟨zᵝ⟩ or ⟨s͡ɸ⟩ and ⟨z͜β⟩. In the otherwise IPA transcription of Shona in Doke (1967), the whistled sibilants are transcribed with non-IPA ⟨ȿ ɀ⟩ and ⟨tȿ dɀ⟩.

Linguistic contrasts among sibilants

Not including differences in manner of articulation or secondary articulation, some languages have as many as four different types of sibilants. For example, Northern Qiang and Southern Qiang have a four-way distinction among sibilant affricates /ts/ /tʂ/ /tʃ/ /tɕ/, with one for each of the four tongue shapes. Toda also has a four-way sibilant distinction, with one alveolar, one palato-alveolar, and two retroflex (apical postalveolar and subapical palatal).

The now-extinct Ubykh language was particularly complex, with a total of 27 sibilant consonants. Not only all four tongue shapes were represented (with the palato-alveolar appearing in the laminal "closed" variation) but also both the palato-alveolars and alveolo-palatals could additionally appear labialized. Besides, there was a five-way manner distinction among voiceless and voiced fricatives, voiceless and voiced affricates, and ejective affricates. (The three labialized palato-alveolar affricates were missing, which is why the total was 27, not 30.) The Bzyp dialect of the related Abkhaz language also has a similar inventory.

Some languages have four types when palatalization is considered. Polish is one example, with both palatalized and non-palatalized laminal denti-alveolars, laminal postalveolar (or "flat retroflex"), and alveolo-palatal ([s̪ z̪] [s̪ʲ z̪ʲ] [s̠ z̠] [ɕ ʑ]). Russian has the same surface contrasts, but the alveolo-palatals are arguably not phonemic. They occur only germinate whereas the retroflex consonants never occur geminate, which suggests that both are allophones of the same phoneme.

Somewhat more common are languages with three sibilant types, including one hissing and two hushing. As with Polish and Russian, the two hushing types are usually postalveolar and alveolo-palatal since these are the two most distinct from each other. Mandarin Chinese is an example of such a language. However, other possibilities exist. Serbo-Croatian has alveolar, palato-alveolar and alveolo-palatal afflicted whereas Basque has palato-alveolar and laminal and apical alveolar (apico-alveolar) fricatives and affricates (late Medieval peninsular Spanish and Portuguese had the same distinctions among fricatives).

Extremely common in languages, such as English, are two sibilant types, one hissing and one hushing. A wide variety of languages across the world have this pattern. Perhaps most common is the pattern, as in English, with alveolar and palato-alveolar sibilants. Modern northern peninsular Spanish has a single apico-alveolar sibilant fricative [s̠], as well as a single palato-alveolar sibilant affricate [tʃ]. However, there are also languages with alveolar and apical retroflex sibilants (such as Standard Vietnamese) and with alveolar and alveolo-palatal postalveolars (e.g. alveolar and laminal palatalized [ʃ ʒ tʃ dʒ] i.e. [ʃʲ ʒʲ tʃʲ dʒʲ] in Catalan and Brazilian Portuguese, the latter probably through Amerindian influence, and alveolar and dorsal i.e. [ɕ ʑ cɕ ɟʑ] proper in Japanese).

Few languages with sibilants are missing the hissing type, but they exist. Middle Vietnamese is normally reconstructed with two sibilant fricatives, both hushing (one retroflex, one alveolo-palatal). Some languages have only a single hushing sibilant and no hissing sibilant, such as southern peninsular Spanish dialects of the "ceceo" type, which have replaced the former hissing fricative with [θ], leaving only [tʃ].

Languages with no sibilants are fairly rare. Most have no fricatives at all oor no fricatives apart from /h/. Examples include most Australian languages, Hawaiian and Rotokas, and what is generally reconstructed for Proto-Bantu. Languages with fricatives but no siblings, however, occur; one is Ukue of Nigeria, which has only the fricatives /f, v, h/.

Contested definitions

Authors including Chomsky and Halle group [f] and [v] as sibilants. However, they do not have the grooved articulation and high frequencies of other sibilants, and most phoneticians continue to group them together with bilabial [ɸ], [β] and (inter)dental [θ], [ð] as non-sibilant anterior fricatives. For a grouping of sibilants and [f, v], the term strident is more common. Some researchers judge [f] to be non-strident in English, based on measurements of its comparative amplitude, but to be strident in other languages (for example, in the African language Ewe, where it contrasts with non-strident [ɸ]).

The nature of sibilants as so-called 'obstacle fricatives' is complicated – there is a continuum of possibilities relating to the angle at which the jet of air may strike an obstacle. The grooving often considered necessary for classification as a sibilant has been observed in ultrasound studies of the tongue for the supposedly non-sibilant voiceless alveolar fricative [θ] of English.

See also

• De-essing
• Plosive consonant
• Shibboleth
• Sj-sound
• Strident vowel
• Voiceless alveolar retracted sibilant
• Voiced apicoalveolar fricative

References

• Shosted, Ryan K. (2006) Just put your lips together and blow? The whistled fricatives of Southern Bantu.