Low
vowels are sometimes referred to by phoneticians as being ‘open’ and high
vowels as being ‘close’, since the aperture of the mouth is wide for open
vowels and narrow for close vowels. The characteristic setting of the mandible
and tongue for each vowel is reflected in the lip position. Generally, low
vowels have a greater lip aperture than high vowels.
In
most languages, vowels have characteristic lip shape as well as aperture. Lip
can be spread, neutral, or rounded; front vowels tend to be spread, and back
vowels rounded. Australian speakers, however, do not reflect this pattern very
clearly. Only the vowels [ʊ,ɔ] and sometimes [u], as in the words put, bought,
and boot, show lip-rounding as a rule. Otherwise all vowels have neutral lip
shape. Lip-reading in Australia, one imagines, is a comparatively difficult
task.
No matter what the dialect, front vowels are never
rounded in English. This is not true of all languages. French and swedish, for
example, have both front and back rounded vowels.
In English, a high back unrounded vowel does not
occur, but in Mandarin Chinese, in Japanese, in the Cameroonian language Feʔ Feʔ,
and in many other languages, this vowel is found. There is, for example, a
Chinese word meaning ‘four’ that is pronounced with initial s followed by a
vowel similar to [ʊ] in regards to tongue position and height but with
non-rounded spread lips. This word is distinguished from the word [sʊ] meaning
‘speed’.
