Seems an obvious point now that you mention it.

Come to think of it I recall having exactly that sort of problem once when I was dabbling in Esperanto. This book was using English words to show how to pronounce the Esperanto sounds, but I pronounced the vowel sounds identically in two words. One was the word 'not', can't recall the other. I thought there was an error and I said so to an Indian friend who, having had both English and American teachers, pointed out that other people pronounce the word differently.

k