Dell XPS 18 (1810, Early 2013) - Manual (Page 26)

Using Headphones/Microphones
Your computer has a headphone/microphone combo port that
supports a headphone, a microphone, or a combo device to listen to
music, record audio, or make voice calls.
WARNING: Listening to loud music for extended periods of time can
lead to hearing loss.
NOTE: It is recommended to keep the volume level low before
connecting the headphones to your computer.
1 Connect headphones to the audio port.
2 Insert the headphones in your ears and adjust the volume level to
a comfortable level.
NOTE: The integrated speakers on your computer are muted
automatically when you connect an audio device to the audio port.
CAUTION: To prevent damage to the headphones when disconnecting
them from your computer, pull the connector and not the cable.
26 │ Using Your Computer