When I used to be in middle school decades ago, I discovered what wonderful tool an English dictionary is. My first dictionary was an Oxford English Dictionary that I inherited from my father, originally published in the 1960s. It had the words, some funny looking alphabet which I later understood was the Phonetic Alphabet, various meanings, synonyms, antonyms and examples of use in sentences.<p>For someone who is intending to build a pronunciation checker, I would start with the words and their International Phonetic Alphabet (IPA) equivalent. With today's text-to-speech technology and machine learning algorithms, going from voice to IPA and vice versa should be quick.<p>Once you have that for words, you could build on it to add evaluation of vocabulary, grammar, sentences etc., A lot of it is around assembling the data and collating training data sets, imo.<p>Cool project!