Meaning: The library was so quiet that you could hear a pin drop.
Choice of Words: Silence: the absence of sound. Filled the air: to occupy or permeate a space.
Alternative Expressions
The library was very quiet.
Meaning: This means that there is not much noise in the library. It is a peaceful place where you can read and study.
Choice of Words: The word "quiet" means there is no noise or very little noise. When you say "The library was very quiet," you are describing a place where there is not much sound.
There was no sound in the library.
Meaning: This means that there is absolutely no noise in the library. It is a very peaceful place.
Choice of Words: The word "sound" means any kind of noise that you can hear. When you say "There was no sound in the library," you are describing a place where there is complete silence.
You could hear a pin drop in the library.
Meaning: This means that the library is extremely quiet. There is so little noise that you could even hear the sound of a pin dropping.
Choice of Words: A "pin" is a small, sharp object that is often used to hold things together. When you say "You could hear a pin drop in the library," you are describing a place where it is so quiet that you could even hear the sound of a pin falling to the ground.