LG Lucid VS840 Owner's Manual page 202

Safety
200
Set the volume in a quiet environment and select the lowest volume at
which you can hear adequately.
When using headphones, turn the volume down if you cannot hear the
people speaking near you or if the person sitting next to you can hear
what you are listening to.
Do not turn the volume up to block out noisy surroundings. If you choose
to listen to your portable device in a noisy environment, use noise-
cancelling headphones to block out background environmental noise.
Limit the amount of time you listen. As the volume increases, less time
is required before your hearing could be affected.
Avoid using headphones after exposure to extremely loud noises, such
as rock concerts, that might cause temporary hearing loss. Temporary
hearing loss might cause unsafe volumes to sound normal.
Do not listen at any volume that causes you discomfort. If you
experience ringing in your ears, hear muffled speech or experience any
temporary hearing difficulty after listening to your portable audio device,
discontinue use and consult your doctor.
You can obtain additional information on this subject from the following sources: