Watch the video that illustrates how Old, Middle, and Early Modern English sound like. Think about what features distinguish Englishes in different historical periods.
Recommended Resources:
Beowulf (700s)
Prologue to Canterbury Tales (1343-1400)
Watch Dr. Handke's (2012) YouTube video to learn about the Great Vowel Shift that happened during the transition from Middle English to Early Modern English.
Prof. William Labov talks about the shift in Standard from a RP (Received Pronunciation) influenced r-less pronunciation to a r-full pronunciation in American English.
This is my favorite podcast on the history of English. The speaker and creator of this podcast is not a linguist but a lawyer. However, his knowledge of the topic is profound. He has a fascinating way of telling the historical and social events that fueled the evolution of the English language. This podcast is highly recommend.