Glottalisation

Closures of voiceless plosives [p t k] and the affricate [tʃ] are often accompanied by glottalisation. This involves the adduction of the vocal folds usually before the oral closure is made. If complete, the adduction results in a glottal stop; if incomplete, there is a portion of creaky voice. Both of these give an auditory impression of the vowel being cut short. This is often called ‘glottal reinforcement’.

Glottalisation is limited to syllable-final voiceless plosives.

Figure 7.9 shows a New Zealand speaker’s production of the vowel + plosive portion the word ‘kit’, with glottal reinforcement. There is a short portion between the segments labelled [+voice] and [–voice] where there is a glottal stop (labelled [?]): in the spectrogram, it shows up as an irregular and distinct vertical striation.

On the waveform, notice the similarly abrupt pulse during that segment; the amplitude drops away more abruptly than in other vowel-to-plosive transitions that we have seen. This abrupt ending to the vowel gives the impression of it having been cut short: voiceless plosives in English are regularly preceded by shorter vowels than voiced plosives, so glottalisation enhances the percept of ‘shortness’.

Glottalisation is especially common with alveolar closure, and sometimes even replaces alveolar closure, when it is known as ‘glottal replacement’. It is less common in conjunction with bilabial or dorsal closure, though there are varieties of English where bilabial and dorsal closure can be replaced by just glottal closure, as in Cockney  for ‘a cup of tea’.