Distinctive Features

The most basic component of a speech sound is a feature, which can be described as the minimal specification that separates one phoneme from another. In fact, a phoneme can be described as a bundle of features, since all phonemes bear at least two or more.

Articulatory features are defined in terms of the amount and type of constriction of air as it travels through the vocal tract.

Consonants

Consonants are described by place and manner of articulation as well as by voicing. When the vocal folds vibrate, the phoneme is said to be ‘voiced.’ [+voice]. The opposite is true when the vocal folds do not come into contact. [-voice].

The place of articulation of a phoneme refers to the area in the vocal tract where an active articulator comes into contact with a passive articulator and includes the terms:

Glottal: (also called laryngeal) the glottis is a combination of the vocal chords and the space between them.

Manners of articulation

This describes the obstruction of airflow as it travels through the oral and nasal cavities and include:

• Stops: total closure with a burst release
• Nasals: no closure; air passes through the nasal cavity
• Fricatives: enough sustained closure to create friction or a ‘hissing’ noise
• Affricates: total closure with a fricative release
• Liquids: partial sustained closure allowing ‘vowel-like’ resonance
• Glides: also called semi-vowels. Little to no closure and highly resonant

Natural Classes

Groups of phonemes can be classified according to places and manners of articulation and voicing. These features are often used to create natural classes of sounds. For instance, the phonemes [p,b,m] all bear the place of articulation feature [bilabial] which distinguishes them from all other phonemes in American English.  The phonemes [n,m,ŋ] all bear the manner of articulation [nasal] which distinguishes them from all other phonemes in American English.   The natural class [p, t, k] can be described as stops which are [-voice].

Acoustic features

bear specific physical properties which can be observed with various machines and computer programs.  Sound wave forms can be observed for    noise content or friction, which is created by fricatives such as[s, z, f, θ].  Sets of phonemes can be categorized by frequencies.  All phonemes which bear the feature [+voice] have a fundamental frequency which is based on the number of vibrations per second of the vocal folds.  Such a set of phonemes would include all vowels, nasals, and liquids.

Auditory features

are defined by how they are recognized by the listener.  For instance a native Spanish speaking listener will perceive the sound /z/ differently from a native English speaker due to the fact that this phoneme does not belong to the Spanish phonemic inventory.

When describing a consonant, list the features in these orders.

For stops, fricatives, and affricates: voicing/aspiration, place of articulation, manner of articulation.

For nasals, liquids, and glides: place of articulation and manner of articulation. Voicing is not mentioned since these phonemes are always [+voice].

For example, [p] would be identified as a voiceless bilabial stop. [n] would be identified as an alveolar nasal. It would be redundant to mention voicing here since the feature [+voice] always applies to nasals in English.

Vowels

Vowel features are described by the height of the tongue in the oral cavity (high, mid, low), the part of the tongue (front, central, back), the position of the root of the tongue (tense/lax; also referred to as advanced tongue root/ATR and retracted tongue root/RTR), and the position of the lips (+/- round).

When describing a vowel, list the features in these orders.

Height, part of the tongue, tense/lax, [+/- round]

For example, [a] would be identified as low, back, tense, [-round].  [U] would be identified as high, back, lax, and [+round].

Many features are binary in their distribution.  This means if a phoneme bears one feature such as [+voice], it cannot bear the other [-voice].  High and mid back vowels in English are always [+round] and front vowels are always are always [-round].   A binary classification is also possible when there are more than two distinctions, one of which is more salient.  Vowel height can be categorized by [-/+low] since high and low vowels are more common in most languages than mid. Thus [high, mid] are classified as [-low].

Features for consonants include:

• Voicing occurs when the vocal chords come into contact with each other.
• Aspiration can be described as a release of a small burst of air.
• Nasality which occurs when air passes through the nasal cavity during production of the phoneme
• Continuants are sounds produced by constant airflow through the oral cavity (mouth).
• Consonantal phonemes include any sound which is not considered a vowel.
• Obstruent phonemes are produced with some sort of obstruction of airflow.
• Syllabics are defined by their ability to stand alone as a syllable.  In English these include vowels, liquids, and nasals
• Labials are produced with one or both lips, such as [v] or [m].
• Alveolar sounds are articulated by the tongue against or near the alveolar ridge (directly behind the upper teeth.)
• Palatals are formed when the tongue is near or touching the hard palate.
• Anterior sounds are formed at the anterior ridge or forward (teeth and lips).
• Posterior sounds are formed at behind the anterior ridge and back (hard palate, velum, glottis, uvula).
• Velars are produced with the tongue near or touching the velum or soft palate.
• Coronals are articulated between the alveolar ridge and the hard palate.
• Sibilants are characterized by the production of noise or air escaping the oral cavity.
• High – when the tongue is high in the oral cavity
• Mid – when the tongue is positioned towards the middle of the oral cavity
• Low – when the tongue is low in the oral cavity
• Front – when describing the position of the tip or blade of the tongue
• Center – when describing the middle section of the tongue
• Back – when describing the back of the tongue
• + Round/- round – referring to the position of the lips
• Tense/lax – These terms are often used interchangeably with ATR/RTR, however this distinction involves more than simply the root of the tongue.  Tenseness can be more generally distributed throughout the oral cavity as well as in a greater area of the tongue.
• ATR/RTR (advanced and retracted tongue root) – when the base of the tongue is forward, lowering the larynx, or retracting the base of the tongue

References

Chomsky, Noam & Halle, Morris (1968). The Sound Pattern of English. New York: Harper and Row.

Clements, George N. (1985). “The geometry of phonological features”. Phonology Yearbook 2: 225–252. doi:10.1017/S0952675700000440.

Flynn, Darin. (2006). Articulator Theory. University of Calgary. http://ucalgary.ca/dflynn/files/dflynn/Flynn06.pdf.

Hall, T. A. (2007). “Segmental features.” In Paul de Lacy, ed., The Cambridge Hndbook of Phonology. 311-334. Cambridge: Cambridge University Press.

Gussenhoven, Carlos & Jacobs, Haike (2005). Understanding Phonology. London: Hoddor Arnold. ISBN 0-340-80735-0.

Jakobson, R., G. Fant & Halle, Morris (1952). Preliminaries to Speech Analysis: the Distinctive Features and their Correlates.. Cambridge, Ma.: MIT Press.

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