Obstruents (plosives, affricates, and fricatives) come in pairs in English. These pairs are listed in the following charts.
|group 1||group 2|
|group 1||group 2|
Traditionally the consonants in group 1 are referred to as voiceless, those in group 2 as voiced. This is certainly what the symbols used to transcribe these consonants suggest. However the difference between these pairs is not always that the first one is voiceless, while the second one is voiced. For this reason we will use the label fortis for the obstruents in group 1 and lenis for the obstruents in group 2. This section gives a somewhat simplified overview of how the fortis–lenis contrast is manifested in various positions within the word. Interestingly, the difference between a fortis and a lenis consonant is not always the same.
voicingIf a sound is voiced, the vocal folds are vibrating. You can watch this in slow motion in the following video.
This vibration is easy to maintain when the air is emerging relatively freely from the lungs. In obstruents this is not so. Plosives and affricates are different from fricatives in that the former contain an occlusion, a phase during their articulation when the flow of air emerging from the lungs is totally blocked. In fricatives the air is continuously escaping because there is a narrow gap between the articulators. But even in fricatives the airflow is significantly slowed down because of the narrowness of the gap. Obstruents with an occlusion are called plosives, those without are fricatives.
VOTVOT abbreviates voice onset time, ie the time vocal fold vibration begins relative to the explosion in a plosive (or affricate). This explosion is called the release of the plosive. If voicing begins about when the explosion takes place, VOT is zero. If it begins earlier, we have negative VOT, if later, VOT is positive. (More on this in Wikipedia.) This makes it possible to distinguish three types of plosive: voiced with negative VOT (vocal folds are already vibrating before the release of the plosive), voiceless unaspirated with zero VOT (vocal folds begin to vibrate at the moment of the release), and aspirated with positive VOT (vocal folds begin to vibrate significantly later than the release).
voiceless sonorantsSonorant consonants (nasals —
aspirated plosivesAt the beginning of a word and at the beginning of a stressed syllable plosives in English are distinguished not by voicing (ie negative vs zero VOT), but by aspiration (ie zero vs positive VOT). Thus the words pin
Plosives occurring between two sonorants (ie vowels or sonorant consonants) are either fully voiced: eg rubber, amber, rebel, abridge; or voiceless: eg rapper, ample, repel, appraise. At the beginning of a stressed syllable, a voiceless plosive is aspirated: repel
word finallyWord final lenis obstruents lose much of their voicing. Word final fortis obstruents are not aspirated: if aspiration is the voicelessness of the following segment, a plosive not followed by anything can hardly be aspirated. What distinguishes a word-final fortis and lenis obstruent is the length of the preceding vowel. If we compare bad and bat, we see that the vowel of bad is significantly longer than that of bat. The same is true in the case of fricatives: the most prominent difference between phase
The following chart summarizes the obstruent allophones in English. Only the labial pairs are given for plosives (