The sound is virtually undetectable to the human ear.

　　這聲音實(shí)際上是人耳難以聽得到的。

　　She leaned over and whispered something in his ear.

　　她探過身去附耳跟他說了些什么。

　　The dog scratched itself behind the ear.

　　狗用爪子撓撓耳后。

　　She whispered something in his ear.

　　她對他耳語了幾句。

　　Hard hats and ear protectors are provided.

　　提供安全帽和護(hù)耳。