Correct pronunciation is often a later step in the process of teaching English as a second language. However, a focus on the correct articulation of vowels can significantly improve listening and comprehension skills as well as articulatory skills. Vowels and consonants differ in their acoustic properties. Unlike consonants, vowel sounds are produced with very little obstruction of airflow, resulting in a difference in the way they sound. Vowels are more sonorous, or acoustically powerful, than consonants, thus we perceive them as both longer lasting and louder than consonants. The greater sonority of vowels also permits them to form the basis of syllables. Introducing the phonetic properties of vowels is relatively easy. Second language teachers can train students to listen for vowel distinctions and teach the articulatory properties of vowels, strengthening students' listening and articulatory skills. Vowels form the nuclei of syllables, thus clarity in vowel sounds helps native speakers better understand foreign speakers. The focus on vowel sounds also supports instruction in the stress patterns of English, allowing students to more easily recognize individual words within sentences. This approach works particularly well with adult speakers who need to be clearly understood in professional settings.