Verified answer

A Hyperbole is simply an extreme exaggeration. That example is one because there is no true physical way for a person to hear another person's heart beat from across a room - but the example is trying to convey how quiet it was by exaggerating it to such a point.

Normal exaggeration: She was the prettiest girl in the world.

Hyperbole: She was the most beautiful girl in the entire history of people.

There is some blur along the line of what is actually exaggeration and what is hyperbole - but usually it will be something that has no possible way of being true.

Another example that you probably hear pretty often: I'm so hungry I could eat an elephant. [or insert any other large animal here].

Hope this helps!