I have a 2006 F-150 and the anoying warning chime is about 30 decibels into the constantly annoying range.
I have done the little wireing trick to disable the chime when the key is in the ignition and the door is open. Simply unplug the black/pink stripe wire.
If you try the old trick of unplugging the connection at the base of the seatbelt on the floor under the drivers seat, both air bags refuse to check on engine start and you get an AIRBAG error.
The actual chime speaker is on the dashboard gague module in a circut board. Lots of time to take the whole dash apart, find the circut board module and drive a screw driver through the speaker.
Has anyone found the secret to turn the bleeping sound off?