Sounds are measured in decibels (dB), this is the force of sound waves against your ear.  Any sound above 85 decibels can cause hearing loss. This is called Noise induced hearing loss (NIHL) It’s not just how loud the sound is, it’s also how long you listen to those sounds. Loudness is affected by how close you are to those sounds too. The closer you are, the louder and more damaging it becomes.
 
If you have to raise your voice to be heard by someone, you are listening to sounds at or above 85 decibels.  If the sounds  reach decibels of 140 or higher, it can cause immediate damage and even pain!
Most MP3 players today have full volume of 105 decibels. At that level, you only have about seven minutes before ear damage begins. That is only a couple of songs!! If you take off your headset and your ears ring or feel different, then you should NEVER use that same volume again. Turn it down! You can still enjoy your music and make sure you’ll be able to hear it for many more years.