I have a 2016 NV 3500 with the tech package. I sometimes hear beeps that sound like they're coming through the car's speakers. I'd like to know what they mean. I know what the speed alert sounds like and I know what the sonar alert sounds like, but this isn't either of those. Sometimes it's three beeps descending in pitch. Other times the pitches are high, low, high (but none of them as high as the speed alert). What are these trying to tell me?