Loud noises damage hearing. Hearing protection must be worn when the noise exceeds 85 decibels.
Hearing protection includes ear plugs, ear muffs or a combination of the two.
A rule of thumb you can use to determine if you need ear protection is if you are standing three feet from a person and have to raise your voice to be heard, you need hearing protection.
Hearing can be easily damaged by loud noises. The National Hearing Conservation Association has many resources ranging from selection of proper protection to when to use it.