I was reading this thread asking if Modern and Early English speakers would be able to understand each other, and also read the section about the evolution of languages in the FAQ, and it got me wondering, what did English sound like before the great vowel shift, or indeed, how did Early and Middle English sound compared to Modern English? And how can we know what they sounded like, without recordings?
You should check the table is this wiki article. From here you can deduce how most of the vowels sounded.
Eg. you see that "time" before the vowel shift is pronounced "i:", and if you (like me) can't read IPA, you simply look for a word than nowadays is pronounced "i:", like "see". So in other words, the "i" in "time" was pronounced like present-day "see".
Also if you know some Spanish or Italian, both languages have maintained the pronunciation of vowels similar to the original Latin.
Here's a highly educational video on exactly that: History of English - The Great Vowel Shift
Also, here's a video about the original pronunciation of Shakespeare's works which was transitional during the vowel shift.
You may also wish to ask the linguists over in /r/AskLinguistics, /r/Linguistics, and /r/AskSocialScience (they get around!).