I'm just thinking aloud here. Modern diesel engines have all sorts of unusual operating modes, including a warm up mode that is designed to heat the catalyst fast. They also burn excess fuel in the exhaust to clean the particulate filter. Manufacturers have some really crazy methods to accomplish these tasks, including unusual injection timing and sometimes restricting intake air via an actual throttle. The noises associated with this operation are unusual and do "freak out" some owners.
Can you try for a better video that captures the sound?
Can you try for a better video that captures the sound?