HP Multimedia Computer User Manual page 6

Component
(5) Audio-out (headphone) S/PDIF jack
(6) Volume mute button
(7) Volume scroll zone
2 Chapter 1 Multimedia hardware
Description
Provides enhanced audio performance, including surround sound
and other high-end audio output.
Mutes and restores speaker sound.
Adjusts speaker volume. Slide your finger to the left to decrease
volume and to the right to increase volume. You can also tap the
minus sign on the scroll zone to decrease volume, or you can tap
the plus sign on the scroll zone to increase volume.
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