Speech Sounds: Classification and Characteristics

Speech Sound Classification

Speech sounds can be categorized into vowels, consonants, and approximants. Approximants (glides: /j, w/ and liquids: /l, r/) share characteristics of both vowels and consonants.

Differences between Vowels and Consonants

There are three main differences between vowels and consonants:

1. Articulatory: Vowels are articulated with a stricture of open approximation (no blockage to the airflow). Consonants are articulated with various degrees of stricture:
   • a) Complete -> plosives /p, b, t, d, k, g, ʔ/
   • b) Close approximation -> fricatives /f, v, s, z,.../
   • c) Open approximation -> approximants /j, w, l, r/
2. Acoustic: Vowels are more sonorous than consonants. There are seven levels of sonority: vowels, glides, liquids, nasals, fricatives, affricates, and plosives.
3. Functional (Phonological Differences):
   • 3.1. Position in the syllable: Vowels are usually the nucleus, but liquids and nasals can also be when they are replaced by schwa.
   • 3.2. Obstruent: Segments produced with enough obstruction to the airflow. Sonorant: Segments with no or little obstruction to the airflow.

Vowel Classification

To describe the position of the tongue during the articulation of vowels in a given language, we use a trapezium. This figure shows the effective area in the mouth in which the tongue can move and change shape to produce different vowels.

A vowel may be described as being:

• Open or Closed
• Back or Front
• Rounded or Unrounded

If the tongue is held away from the roof of the mouth when a certain vowel is articulated, then that vowel is called open. If the tongue is held close to the roof of the mouth, then we speak of a closed vowel. We also use the terms half-open and half-closed.

If the front of the tongue is raised towards the roof of the mouth during the articulation of a vowel, it's a front vowel; if the back of the tongue is raised, it's a back vowel. There are also central vowels, which are pronounced with the center of the tongue raised. Regarding lip-rounding in vowels, back vowels are normally rounded.

Quality vs. Quantity

• Quality: The position of the tongue in the oral tract during the articulation of a vowel.
• Quantity: The length (duration) of a vowel.

Diphthongs

A diphthong is a long vowel with a single, noticeable change of quality during one syllable. The tongue starts moving from the position to articulate the first vowel to the position for the second vowel in a rapid sweeping movement.

A diphthong may be described as being:

• Rising or Falling
• Centring, Closing or Opening
• Wide or Narrow

Rising diphthong: The second element is more prominent than the first. Falling diphthong: The first element is more prominent than the second. All nine major English diphthongs are falling.

If a diphthong is centring, it ends in schwa (e.g., here, there, tour). If a diphthong is closing, the tongue moves from a more open position to a closer one, and if it is opening, the reverse happens. The diphthongs (eɪ, aɪ) are closing. If the tongue makes a wide, sweeping movement, as in the diphthong (aɪ), in which there is a change from the very open position of (a) to the much closer position of (ɪ), then we speak of a wide diphthong. If there is little tongue movement, as in (aʊ), the diphthong is narrow.

Consonant Classification

There are three main parameters for classifying consonants:

1. Voicing: Voiced vs. devoicing is the sound change produced by the influence of the phonological environment.
   • Voicing: A voiceless sound can become voiced before a vowel.
   • Devoicing: Voiced sounds can become voiceless in syllable codas.
2. Place of Articulation (PoA):
   • Bilabial (upper lip + lower lip)
   • Labio-dental (upper teeth + lower lip)
   • Dental (tongue + upper teeth)
   • Alveolar (tongue + alveolar ridge)
   • Post-alveolar (tongue + near of alveolar ridge)
   • Palato-alveolar (tongue + hard palate)
   • Velar (back tongue + velum)
   • Glottal (glottis)
3. Manner of Articulation (MoA):
   • Plosive: If there is complete obstruction of the mouth passage.
   • Fricative: If there is narrowing of the air passage.
   • Affricate: If the air is completely blocked and released slowly so that friction is heard.
   • Nasal: If the air passes through the nose.
   • Approximants: Liquids (/l, r/) and glides (/j, w/).