Dodge 2011 Grand Caravan - Manual (Page 186)

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 System Off
Slow Tone
184 UNDERSTANDING THE FEATURES OF YOUR VEHICLE