T  h  i  n  k    hard,  work
The ears are sensitive instruments, able to detect sounds as small as clothing rubbing against skin.   When exposed to continuous loud sounds, muscles inside the ears can contract to prevent damage to these sensitive organs.   However, a sudden loud sound can break an eardrum before the sound can be heard, and permanent nerve damage is another possible consequence of exposure to sudden loud sounds.
Earplugs of compressible foam as well as headphone-style ear protectors are possible options for protecting hearing.
Use of power tools, use of hammers, and close proximity to other loud sounds or machinery are examples of situations where ear protection is warranted.
Don't wear more ear protection than is required, because hearing protection also can prevent warning sounds from being heard.