In England between the middle ages and the modern era, the pronunciation of long vowels changed both utterly and methodically. Meanwhile spelling sort of lagged, which is why spelling and sound are so adrift in English.
In the Middle Ages 'long' vowels really were just long-drawn-out versions of other vowels. So 'child' was pronounced like 'chilled', but with the vowel drawled for longer. Then, possibly as a result of the black death and the breakdown of class distinctions, the loss of French, whatever, these long smooth vowels became harder and broken. Something like 'cheyuld', or 'choyuld'. In parts of England (such as the black country) there are people who still have this accent. And then eventually the broken vowel smoothed out again, into standard modern pronunciation 'ch-eye-ld'.
Anyway, there's an excellent website where you can hear people talking in the accents of the different centuries:
Middle English| 1450 to 1550 | 1550 to 1650 | 1650 to 1750
In those examples the older male voice represents the older fashioned accent, and the young woman a more 'modern' speaking style that developed in that century.