Here's how it works:
* Implicit comparison: The sentence doesn't explicitly state "like" or "as" to make the comparison.
* Simile structure: The sentence uses the word "as" to indicate a comparison between the audience becoming quiet and the character speaking.
The implied comparison: The sentence suggests that the audience becoming quiet is similar to or comparable to the character speaking. This comparison is implied because we understand that the character's speech often has the effect of silencing the audience.