When you eat something crunchy and it's so loud in your head that you are unable to hear what anyone around you is saying. This may be intentionally used as a manner of shutting out the world or simply an unfortunate consequence of cacophonous cuisine.
Teacher: "Can you answer this question?"
Student: "My apologies, I was in the throes of crunchy isolation. What was your question again?"
Teacher: "Who wrote Fed 51?"
Student: "Maybe I should have stayed in my crunchy isolation..."