Subaru Impreza 2017 Owner's Manual page 89

List of buzzer sounds
Buzzer sound Status Reference page
Refer to page 73.
Two-tone beep Lead Vehicle Start Alert is active*.
*The buzzer that indicates when a lead vehicle is detected or when it is no longer detected
(Lead Vehicle Acquisition Sound), as well as the Lead Vehicle Start Alert can be turned on
or off.
Refer to page 90.
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