Each language has parameters concerning the distribution of plosives. Some languages only permit voiceless plosives, e.g., Proto-Quechua, whereas others permit both voiced and voiceless, e.g., Spanish. Still others allow a 3-way distribution of plosives, adding aspiration to the mix, e.g., Hindi. (Aspiration is symbolized by the diacritic [h].)
- [pʰəl] ‘fruit’
- [pəl] ‘moment’
- [bəl] ‘strength’
When the features of voicing and aspiration are exchanged in identical phonological environments (here word-initial), the meaning is also. In languages such as Standard French, aspiration not an acoustic feature. For example, there is no difference in meaning between [tas] and [tʰas] ‘cup’. Articulating the word with an aspirated /t/ will quickly reveal that French is not the speaker’s native language!
In other languages such as Standard English and Farsi, aspirated plosives exist, but only as allophonic variations of those that are [-voice]. This means aspirated plosives will only surface in specific, rule-driven phonological environments with the speaker unaware of producing them. In Standard English aspirated plosives are only found as an allophone of voiceless plosives in word-initial position, e.g., [tʰun] tune and in onset position of a stressed syllable, e.g., [ə .tʰen] attain.
Here is an exercise to help you recognize the phonological environments in which aspirated stops surface in Standard English. Phonetics: Aspiration 1.1
Voice Onset Time
Voice Onset Time or VOT refers to the lapse of time that occurs between the release of a stop/plosive (in Standard English /p,b,t,d,k,g/) and the beginning or onset of a vowel sound. In other words, in the articulation of a word such as /pat/ pot, there is a point at which the release or end of the articulation of /p/ transitions into the vowel sound /a/. This is the phonological environment in which VOT is observed.
VOT is measured in milliseconds and is referred to as either negative, zero, or positive, referring to voiced, voiceless, and aspirated plosives respectively. These acoustic features are measured with a spectrogram, a visual representation of a speech sound in which the transition from the plosive release or burst to the onset of the vowel or periodicity is depicted in formants and frequencies.
So let’s break this down.
Negative VOT occurs when the plosive release overlaps with the onset of vocal fold vibration, e.g., voiced plosives. /bajk/ bike Since these adjacent phonemes share the feature [+voice], the production of the vowel begins early in the plosive release.
(3) /b/ /a/
release of plosive onset of voicing
(3) shows the onset of the vowel /a/occurring before the release of /b/. Below is a spectrogram of /b a/.
The red frame shows that the vocal cords begin vibrating (the onset of /a/) before the plosive is released at approximately 200 ms.
Zero VOT refers to when the plosive release occurs at approximately the same time as the onset of vocal fold vibration, e.g., voiceless plosives. /spat/ spot Due to the fact that these adjacent phonemes do not share the feature [voice], there is a distinct transition as the production of the vowel begins at the moment of the plosive release.
(4) /p/ /a/ release of plosive onset of voicing
In (4), we see that the plosive release and the onset of the vowel occur quasi simultaneously.
Here the red frame shows that there is no lapse between the release of the plosive and the onset of the vowel.
Positive VOT describes the lapse of time that occurs between the plosive release and the onset of vocal fold vibration, e.g., aspirated plosives. /pʰat/ pot. In the production of an aspirated plosive, a burst of air accompanies the release thus forcing the onset of the vowel to occur several milliseconds later. Below is a visual that may help you better understand the transition period between the plosive release and onset of the vowel.
(5) /pʰ/ /a/ release of plosive onset of voicing
Here the red frame captures an initial release of /p/ followed by several ms. of aspiration, after which the voicing of the vowel commences.
The study of VOT is has been crucial in research related to segmental contrast, language acquisition, and language impairment.
Click here to access an excellent overview of the acoustic properties of all English (Australian) consonants.