Prado 120 3L Diesel 1KD Sound has changed

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Hey, I've got a 2008 Prado 120 D4D Diesel ( 1KD ) and it's got 62000KM has been dealer maintained and recently around 500km ago it has suddenly got a different type of tone to it seems like it's become quieter but it's got a sort of whistle sounds it's had one since it was new but it's not the same, according to the dealer all checks out tho they did replace the drive belt but that reduced the squeak it had when wet.
looking for any input on what to check or is this how it's meant to sound
It runs perfectly no smoking or anything power output is great too.
I'm looking to attach a video but I'm not sure how to do that