Vowels are described as open speech sounds because there is no obstruction to the flow of air from the lungs as it passes up through the trachea, through the larynx, through the oral cavity and out of the mouth. Other than a speaker positioning the tongue, jaws and lips in a specific configuration, there is nothing to obstruct the airflow. As such, they contrast with consonants – which are known as closed sounds because, unlike vowels, there is some form of obstruction to the airflow through the vocal tract.
In addition, vowels are oral sounds, i.e. made with air escaping only through the mouth. Further, they are voiced, being produced with the vocal folds vibrating. They most commonly appear as the nucleus of a syllable. As we will see, vowels can minimally be described in terms of the openness of the mouth, the position of tongue elevation, and the shape of the lips.
In this section we will consider the following topics:
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