The tone of the sentence, How did you not know that, is meant (and heard) as demeaning and belittling. Even inserting may into a sentence, such as "You may not have known this, but (with explanation)" is better than the first way. Using "may not have known" gives more respect for what the person does know.
Example:
You may not have known that you have to attach the cords in a particular order for the printer to work.
Her voice had that tense, strained tone that I know so well.
The tone of a sentence can be conveyed through the choice of words. For example, a sentence that uses formal language and polite phrasing may have a respectful tone, while a sentence with abrupt language and strong directives may have a commanding tone.
I don't like your tone of voice.
There was a very mean tone in his voice when he spoke.
We analyzed the author's tone in the book.
Because the structure is tone
The sentence does not provide any specific information about the narration style, tone, or point of view. It is ambiguous and lacks context for any assumptions to be made about the narration.
a strident tone in his writings.
Careful now Tim, you're getting a little raunchy there. Why don't you tone it down? There are kids here you know.
You know, these kinds of things just make me shake my head and wonder.
Tone isn't something with one right answer - it's based on how the writer makes you feel. This sentence makes you think the writer is looking forward to seeing the person, so it could be called a friendly tone or an excited tone or even an anticipatory tone.
To change the meaning of sentence when it is typewritten, use bold on the word you want to stress. For example:Don't talk to me in that tone of voice.Don't talk to me in that tone of voice.Don't talk to me in that tone of voice.