After the vehicle was parked and powered off for several hours, I started the truck and experienced an extreme and unexpected audio volume spike from the factory BOSE sound system. The startup sound and turn-signal chime played at an excessively loud level, far beyond normal operation. The sound was sudden and intense, causing immediate ear pain, ringing, and a headache. My dog, who was in the vehicle, became visibly distressed and shaken by the noise. This volume spike occurred before any media audio was playing and appears tied to the vehicle's startup and chime audio system, not user-adjustable radio volume. The turn-signal clicking remained extremely loud afterward, indicating the same audio channel was affected. The vehicle has been operating normally prior to this incident and had not been modified in any way. This occurred during normal use of a brand-new vehicle (purchased about a month ago) with no warning lamps/messages/ or other symptoms prior to the incident. The problem has been reproduced and was able to be recorded via phone video during a reproduction attempt to provide to dealer.