Safety Belt Warning Chime
WARNING: This page is about a different car, the 2009 Ford Mustang. However, it is still accessible from the selected car via links, so may be relevant.
The safety belt warning chime is activated when the ignition switch is in the RUN position and the RCM detects an unbuckled driver safety belt. The instrument cluster (IC) generates the chime for a duration of 6 seconds or until the safety belt is buckled.