Onomatopoeia is the formation of a word from a sound associated with what it is named. Examples include:
* Bang
* Meow
* Buzz
Silence is the absence of sound, so it cannot be a sound itself.
While "silence" itself isn't onomatopoeia, you could use other words to describe the *feeling* of silence, which might be considered onomatopoeic. For example:
* Hush
* Shhhh
* Quiet
These words create an association with the feeling of silence, though they aren't directly replicating the sound itself.