Vowel + nasal sequences

In vowel + nasal sequences, nasality starts early and is slow compared to the onset of the closure in the vocal tract, meaning that there is a period of oro-nasal airflow. A common sequence is: oral airflow only (i.e. velum raised, allowing air to flow out of the mouth only); oro-nasal airflow (i.e. velum lowered, vocal tract open, allowing air to flow out of the mouth and nose); nasal. This description slightly misleadingly suggests that there are three discrete segments. In the middle part, the nasal airflow gradually increases, so that the transition from oral to nasal is generally quite smooth. Individuals’ (and dialectal) co-ordination of the velum lowering and the formation of the oral closure is variable: some speakers lower the velum rather quickly and the vowel + nasal sequence is more like a reflection of the nasal + vowel sequence.

Figure 9.3 represents vowel + nasal sequences schematically. The lowering of the velum is represented as starting early, and happening slowly.

Figure 9.4 shows the vowel + nasal portion for a male Australian English speaker saying the word ‘hang’.

The vowel + nasal portions are much less distinct than in the case of nasal + vowel sequences. F1, around 1000 Hz, gently falls, but its amplitude fades away too (that is, it gets lighter in color on the spectrogram). The waveform has a smooth diminuendo, and the amplitude falls off gradually. F2 and F3 come together into a pattern distinctive for velars at around 0.87 s, where the boundary between [a] and [ŋ] is marked, and then they fade away in amplitude and are no longer visible.

The nasalization of vowels before nasal consonants is an example of anticipatory co-articulation: a vowel anticipates a later sound (in this case a nasal) by adopting some aspect of the production of the later sound.