Louder engine noise - video

[goral]

Hi
I've been hearing louder engine running for 2 days.
Is like low bass -see video-
And is noticed practically only inside car.
Any ideas what to check first?
I can only hear this when car is idling, no accelerating.

VW Golf mk6 Diesel 1.6 TDi Variant (AJ5) -2012-

https://www.youtube.com/watch?v=YP_gr321wmM

Noise when I accelerating:
https://www.youtube.com/watch?v=PzClyf7ZeIs

And engine - loud video -
In right side, is very noticeable whistling sound.
https://www.youtube.com/watch?v=LwF_Vv0ZOFk