为了解释气囊如何改变声音，de Boer博士制作了口腔、舌和喉的塑料模型，并压入空气使之发出不同的元音。

To find out how having an air sac changed the sounds produced, Dr DE Boer created plastic models of the mouth, tongue and throat and forced air down them to produce different vowel sounds.

youdao

为了规范元音的发音，言语学家创造了语音图，即语音口腔剖面图，使瞧不见、摸不着的差别元音有了明确的发音定位。

In order to standardize pronunciation of vowels, phoneticians invented a diagram illustrating the side view of oral cavity and showing clearly the pronouncing positions of different vowels.

youdao