What does 20 decibels sound like?

Question

How about 30? 13?

The reason I ask is because I am buying a new fan for my computer.

Answer 1

It sounds vewy vewy qwiet.

According to [1], 30 dB is roughly the sound of a whisper in a quiet library. At 20dB it will be quieter than most of the ambient sounds in a normal household [2], whereas 13 dB will be just tiny bit more noisy then rustling leaves or the interior of a broadcasting studio.