AccentTraining – William Shatner

This app is designed to help English language students learn to understand vowels. You can choose multiple accents and speakers for these accents as well as the length of the training course.
  We have found that language students who complete 5 to 10 long courses in a few days can significantly improve their vowel recognition rate. It works by asking the user for the identification of a particular vowel. The user’s troublesome sounds will appear more frequently.