A noise when engine started?

Be in Peace Gentlemen.

The actual model is B250 with a 7 speed Dual Clutch Transmission.
when start engine, intermittent come a special noise, record the follow video, the Gear is still at Park
1st video outside
2nd inside to see the engine speed from 1100 to 770 around 3 minutes.
https://www.youtube.com/watch?v=LkPJI1pUFeY

https://www.youtube.com/watch?v=H33PgF0jvTg

Question:
Where is the noise possibly coming from besides the engine noise when the gears is still in park position?

someone said the transmission should be replaced, but when I run it on the road, the transmission switch normal, the noise beside the engine sound intermittent come no matter the gears switch

Just a DIY customer, thank you any idea!