On being ill-at-ease in the land of one's bith.

I hear a sentence.  It is recognizably a sentence of my mother tongue.
I know the grammar, vocabulary.  The speaker's pronunciation presents no difficulties.

And, yet, I don't know what the hell they are saying.

At best, their sounds resound like a noise in an empty room; there is no context to support understanding.

At worst, I am horrified to imagine what the surrounding thoughts and emotions actually are--I listen with a feeling of revulsion and disgust.