Speech sound production

 

The articulatory description of speech sounds

All articulatory descriptions of all speech sounds, ie. consonantal and vocalic, must answer the same six questions:

1. Type of airstream - pulmonic, glottalic or velaric?

2. Direction of airstream - ingressive or egressive?

3. Vocal fold vibration - unvoiced or voiced?

4. Velum raised or lowered - oral, nasal, or nasalised?

5. Point of Articulation - labio- dental, velar etc.?

6. Mode of Articulation - plosive, fricative etc.? What is the nature of the point of closure or approximation in its influence on the airstream as the air passes through the oral cavity or the nasal cavity? [mode of articulation]

The articulatory description is as follows:

[+/- pulmonic] [+/-egressive] [+/- voice] [+/- oral] [Point of Articulation] [Mode of Articulation]

For example, [ ] is described in the following articulatory terms: pulmonic egressive voiced bilabial plosive

and [ ] as: pulmonic egressive unvoiced labio-dental fricative

This is for general phonetics; when we come to English sounds we see that all of them, are produced on a pulmonic egressive airstream. For this reason, the first two parameters of the articulatory description are usually omitted.

For example, [ ] is described in articulatory terms simply as a voiced velar plosive

Question #1 - Type of airstream

Is the airstream pulmonic - initiated by the lungs - or non-pulmonic? [+/- pulmonic airstream]

Most speech sounds in Indo-European phonological systems, with the exception of some speech gestures, are produced on a pulmonic airstream.

Question #2 - Direction of airstream

Is the airstream egressive - from the inside of the body to the exterior - or ingressive? [+ / - egressive airstream]

Most speech sounds in Indo-European phonological systems, with the exception of some speech gestures, are produced on an egressive airstream.

Question #3 - Vocal fold vibration

Do the vocal folds vibrate during the production of the speech sound - is it voiced or unvoiced? [+ / - voice]

As the pulmonic egressive airstrean passes through the glottis, do the vocal folds vibrate or not.

If the vocal folds vibrate, then the resulting sound is said to be voiced.

If the vocal folds do not vibrate, then the resulting speech sound is said to be unvoiced.

All vowels are voiced.

All nasals are voiced.

All the prosodic features take place on voiced sounds.

Not all consonants are voiced.

We understand strings because we are able to segment them.

Since some sounds are voiced and others are not voiced, a string of segments (speech sounds) constitutes a binary sequence, for example, [ + - + + - + - - + + - + - ]

In a sense, speech is a sort of digitalised sequence, a binary system comprising voiced and devoiced elements.

The system of voicing and devoicing is fundamental to the function of speech sounds as meaningful signals.

The binary opposition - voicing / devoicing - makes strings meaningful.

 

Question #4 - Velum raised or lowered?

Is the velum raised - blocking off the nasal cavity or lowered -giving access to the nasal cavity? [+ / - nasal]

If the velum is raised during the passage of the pulmonic airstream, the speech sound will be oral.

If the velum is lowered during the passage of the pulmonic egressive airstream, the speech sound will be nasal or nasalised.

In order for nasalisation to occur, the pulmonic egressive airstream will pass out of the body through both the oral and nasal cavities.

 

The Points of Articulation

Which organs and which points of closure - or approximation - are instrumental in the production of the speech sound?

The first articulators moving from the front of the oral cavity are the lips and the first point of articulation is bilabial.

i. Bilabial sounds - the two lips are brought together to form a point of closure.

[ ]; [ ]; [ ] - no tongue

ii. Labiodental sounds - the upper teeth are brought into contact with the lower lip, the air escapes through the gaps between the teeth - the labio-dental forms an imperfect closure.

[ ]; [ ]; [ ] - no tongue

iii. Interdental sounds - there is an interdental sound when the tip of the tongue is placed between the upper and lower teeth.[

iv. Dental sounds - the tip of the tongue is placed behind the teeth.

[ ]; [ ]

v. Alveolar sounds - the tip of the tongue forms a point of closure or a point of approximation with the alveolar ridge.

[ ]; [ ]; [ ]; [ ] - alveolar lateral approximant - tongue

vi. Post-alveolar - the blade of the tongue is raised to a point of approximation with the post-alveolar region.

[ ]; [ ]; [ ] - median approximant - tongue

vii. Palato-alveolar - the front of the tongue is raised towards the palato-alveolar region, forming a point of approximation.

[ ]; [ ] - tongue

viii. Palatal - the front of the tongue is raised towards the hard palate, forming a point of approximation.

[ ] - tongue

ix. Velar - the back of the tongue is raised to form a point of closure with the soft palate.

[ ]; [ ]; [ ] - tongue

x. Glottal - the air passes with force through a partially open glottis.

[ ] - no tongue

 

Points of articulation which involve the tongue as an articulator i.e. the tongue is instrumental:

dental - tongue / back of upper teeth

alveolar - blade of tongue / alveolar ridge

post-alveolar - blade of tongue / post-alveolar region

palato-alveolar - front of tongue / palato-alveolar region

palatal - front of tongue / hard palate

velar - back of tongue / soft palate

 

The Modes of Articulation

The mode of articulation is a result of the influence of the configuration of the organs in the vocal tract on the airstream as it passes through the oral cavity or the nasal cavity (or both).

The human perception faculties can distinguish certain modes of articulation, which enables us -as human beings- to determine distinctive qualities of sounds according to their mode of articulation - i.e. listeners can perceive a differencce between plosives and fricatives.

The ability to identify differentiated modes of articulation provides a further basis for segmentation in strings of speech sounds and constitutes a fundamental criteria in phonemic analysis -phonemes.

The identification of phonemes in a language is explicitly based on modes of articulation.

At a phonemic level, we can differentiate between plosives and fricatives, in the same way as we can differentiate between a bilabial articulation and a velar articulation.

There is one major criteria for the analysis of modes of articulation, that is the degree of approximation of one articulator to another in the oral cavity during the production of a specific sound.

There are 4 basic degrees of approximation:

1. complete closure

2. intermittent closure

3. partial closure

4. narrowing

According to the degree of approximation during the passage of the airstream, so the mode of articulation of the sound will vary.

1. Complete closure

In order to achieve complete closure, the articulators are brought into firm contact, so that no air can pass in either direction.

If the airstream is egressive and is obstructed in the oral cavity by a point of closure, this will produce a specific quality of sound, usually a plosive.

e.g. plosives (stops), affricates, nasals.

2. Intermittent closure

Complete closure is followed by release - separation of the points of articulation - and this is repeated in rapid sequence.

(a) rolled "r" [ ]

(b) flap [ ]

3. Partial closure

It is achieved when the mobile articulator moves towards the static articulator as if to form complete closure, but it is withdrawn abruptly before contacting the static articulator.

The resulting sound is called an approximant.

2 types:

[ ] - median

[ ] - lateral

4. Narrowing

Narrowing is achieved when articulators are brought into close proximity but do not touch as the airstream passes between the articulators - molecules of air vibrate, which is perceived as friction or noise.

If the airstream is egressive and passes through a point of approximation, then, the resulting sound will have a distinctive and different quality, usually a fricative.

This mode of articulation produces fricatives or affricates (affricates combine 2 modes of articulation).

 

Description of consonants and vowels

Consonantal and vocalic speech sound production mechanisms are usually sub-divided into different types or modes of articulation.

In terms of articulation, there is no need to distinguish between consonantal and vocalic speech sounds.

Nasal, approximant and vowel articulations share many common characteristics, for example, they are all voiced.

Nasals are similar to plosives in that both are produced by a point of closure.

However, a distinction is usually made between consonants and vowels.

Individual sounds are called segments.

A sequence of segments in speech communication is called a string.

For convenience, segments are usually discussed in terms of two major divisions:

i. vowels

ii. consonants

We should take note that it is a theoretical division and it is for a scientific use, that is, for our theoretical convenience.

There is no intrinsic difference between a consonantal and and a vocalic sound - both are speech sounds produced on an airstream.

All speech sounds can be described using the same articulatory criteria, that is, irrespective of whether they are considered to be vowels or consonants.

The main difference between the production of vocalic and consonatal sounds is that consonants are described in terms of the configuration of the vocal organs (point of articulation) during the passage of the airstream, e.g. the tip of the tongue is touching another articulator as the airstrean passes out of the body, whereas vowels are described in terms of the shape of the space in the oral cavity during the passage of the airstream.

While the description of consonatal sounds identifies the movement of the articulators and the configuration they move into prior to and during the passage of the airstream, the description of vocalic sounds identifies the movement of the articulators and the configuration they move into and out of because it is the configuration of the articulators in the oral cavity which determine the shape of the space in to the oral cavity during the passage of the airstream.

Consonants are fairly adequately described by an articulatory description while vowels require the description of the shape of a space which is not so readily achieved.

That is why we differentiate between the description of consonants and the description of vowels.

 

Sound production mechanisms

There are 5 major modes of articulation:

i. plosives

ii. fricatives

iii. nasals

iv. approximants

v. vowels

 

Consonatal mechanisms

 

i. Plosive mechanism

In order to achieve any plosive sounds, two articulators are brought into contact, forming a point of closure.

The airstream, usually generated by the lungs - i.e. pulmonic- is stopped in its passage through the oral cavity.

This causes an increase in air pressure behind the point of closure which is called compression.

Then, the articulators are separated so that the compressed air can pass freely out of the body. This is called release.

 

Plosive mechanism formula:

point of closure + (voiced)(unvoiced) pulmonic airstream = compression + separation of articulators = release = plosive sound

 

ii. Fricative mechanism

In order to produce a fricative, the articulators are placed in close proximity one to the other, forming a narrowing.

As the airstream (which is usually pulmonic) passes through the narrowing on its way out of the body, the molecules of air vibrate at the point of articulation (i.e. narrowing) which is perceived as friction (or noise, i.e. irregular sound waves).

 

Fricative mechanism formula:

narrowing + (voiced)(unvoiced) pulmonic airstream = vibration (generates irregular sound waves perceived as friction / noise) = fricative sound

 

iii. Nasal mechanism

In order to produce a nasal sound, the articulators are brought into firm contact creating a point of closure in the oral cavity.

The pulmonic airstream (passes through partially closed vocal folds, causing voice) passes into the oral cavity, but since it is obstructed by the point of closure and given that the velum is lowered, the air passes out of the body through the nasal cavity (there is a point of closure as in the production of plosives, but there is no compression or release - air passing out of the body through the nasal cavity).

 

Nasal mechanism formula:

Point of closure in oral cavity (velum is lowered giving access to the nasal cavity) + voiced pulmonic airstream = brief compression behind point of closure in oral cavity = escapes through nasal cavity (made possible by lowered velum) = nasal sound

 

iv. Approximant mechanism

A part of the tongue is brought into slight contact or into close proximity with a second articulator.

Pulmonic air (passes through partially closed vocal folds), into the oral cavity, over the surface of the tongue and out of the body.

During approximant production, the tongue may move into a slightly different position.

 

Approximant mechanism formula:

Point of slight contact or close proximity + voiced pulmonic airstream + slight variation in tongue position + air escapes over surface / sides of the tongue = approximant sound

 

Vowel mechanisms

 

i. Vowel mechanism

The tongue moves into one of the following configurations:

high / front [ ]

high / front centralised [ ]

mid / front [ ]

low / front [ ]

low / back [ ]

low / back centralised [ ]

mid / back [ ]

mid / back centralised [ ]

high / back [ ]

high / back centralised [ ]

central [ ]; [ ]

 

Pulmonic air passes through partially closed vocal folds, into the oral cavity, over the surface of the tongue and out of the body.

Tongue configuration changes during the passage of the pulmonic airstream can result in glides (diphthongs, triphthongs and semi-vowels)

Vowel mechanism formula:

Specific tongue configuration (which determines the shape of the space in the oral cavity) + voiced pulmonic airstream = vowel sound