For those of you who hate absolute silence in your classroom, or just want to embrace your inner nerd a bit more, there is a fantastic website called ambient-mixer.com.
There, you can listen to the sounds of Gryffindor's Common Room or Bilbo Baggins' Home. You can also just listen to nature sounds and other ambient sounds. The best part is, you can create your own mixes!
How fun would it be to allow your students to create an ambient mix for tests and seat work? Or even for a book setting?