How does Hemingway indicate tone in "Hills Like White Elephants"?

To a certain degree, tone is subjective. In stories, as in real life conversations, people can misinterpret one another's tone, leading to subtle or overt conflict. In fact, much of the power of this story depends precisely on this sort of dynamic of misreading and misinterpretation between the two main characters.

Much of the tone in the story is created by the awkward silences between the two characters. Another way Hemingway creates this sense of awkwardness or discomfort is by what is sometimes called "non-responsive" dialogue or talking at cross-purposes. In other words, one character will make a comment, and rather than the other character responding directly, the second character will pause and then say something completely irrelevant. This gives the impression that the characters are not communicating, adding to the awkward, uncomfortable tone of the conversation.

Finally, the short, declarative sentences add to the awkward tone and sense of unresolved tension. The spareness of the description also contributes to the intensity of the unspoken emotions, just as a neutral backdrop will make a striking visual image stand out.