* Simile: A simile uses the words "like" or "as" to compare two things.
* Metaphor: A metaphor directly states that one thing is another thing, without using "like" or "as."
"Hushed as death" uses the word "as", but it's comparing the state of being hushed to the state of being dead. It's not comparing two things.
This phrase is actually a metaphor, implying that the hush is so profound and still, it's like death itself.