Sound Settings - Sony PlayStation Portable PSP-1004 Instruction Manual

Sound Settings

You can turn off the key tone and limit the volume level.
AVLS (Automatic Volume Limiter System)
You can limit the maximum volume. This can help prevent sound escaping
from the Headphones as well as the possible danger resulting from being unable
to hear what is going on around you when wearing Headphones.
Off
On
The default setting for the menu item is underlined.
Key Tone
You can turn off the key tone (the confirmation sound made when you press a
button).
Off
On
The default setting for the menu item is underlined.
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Sound Settings
Does not set a limit; allows for the volume to be adjusted manually
Sets a limit on the volume
Does not make a confirmation sound
Makes a confirmation sound