Vowel Border

You know the rule for ship and sheep. Your ear still hears one word. Vowel Border trains the ear itself: hear the two sounds from several voices, then prove you can tell them apart.

THE MAP
21 borders between similar English vowels, grouped the way learners confuse them: ɪ / i:, æ / e, ɔ: / ʌ, u: / ʊ, ɜ: / ʌ, diphthongs (aɪ / aʊ, eɪ / e, oʊ / ɔɪ), r-colored vowels (car / care, beer / bear, core / cure) and triphthongs (hire / hour). Each border is colored by your score, so the map is your plan.

TRAIN
• Five word pairs per border, side by side: ship | sheep, bad | bed, pull | pool.
• Tap a word to hear it; Play all reads every pair in turn, pairs or one side first, on repeat if you like. One voice per visit, with a chip that switches to the next one.
• IPA and a one-line mouth cue for each sound. Speed 0.8 to 1.0.

QUIZ
• Ten trials per round. AB: one word plays, tap the one you heard. ABX: two references, then a third word; which did it match? Borders without minimal pairs ask which sound you heard.
• Every answer shows which word it was, then the next one plays. Words are prepared ahead, so nothing stalls mid-round.
• ABX unlocks when a border passes 70 %.

MANY VOICES, SAME WORD
A single speaker teaches you that speaker. Vowel Border takes a new voice from the English voices installed on your iPhone every round, or every word if you prefer, so the contrast survives a change of talker. US voices are on from the start; UK, Australian and other accents are there to switch on when you want them. The quiz never asks a contrast a voice does not make. Preview voices and add more from Settings.

HONEST RESULTS
Score per round, each border's score before and after, and the words you missed with the voice that spoke them. History by day and by border. No streaks, no points.

OFFLINE AND PRIVATE
No account, no sign-up, no ads, no tracking. The words are spoken by your iPhone's own voices; your results stay on your iPhone. Works in airplane mode. Optional daily reminder.

Word pairs were checked against the CMU Pronouncing Dictionary (Carnegie Mellon University). Interface in 20 languages.