The act of putting headphones in or on one's ear so as to obstruct their ability to perceive auditory cues from their outside environment.

Advance notice of something that will need attention.

1. advance notice

2. a warning

To give someone a warning of iminent danger, trouble or strife.

To fight someone 1 on 1 with no one else getting involved

Exclamatory warning indicating that one practice increased alertness to avoid harm from a pressing threat.

a warning, especially of danger or the need to be alert