Jeep 2011 Liberty - Manual (Page 179)

The system will indicate a detected obstacle by showing
three solid arcs and will produce a one-half second tone.
As the vehicle moves closer to the object the EVIC
display will show fewer arcs and the sound tone will
change from slow, to fast, to continuous.
Park Assist Off Slow Tone
3
UNDERSTANDING THE FEATURES OF YOUR VEHICLE 177