That article is a couple of years old now and was referring to the 3.0d and even admits that the twin turbo variant (3.0sd) is quieter.

If you're a US resident, it's almost pointless talking about the 3.0d when making comparisons because you won't get it on the market there - you'll get the latest, quietest version of the 3.0sd.

The 3.0sd isn't noisier than other brands in my opinion. I test drove the diesel ML/G 280/320 and the Audi Q7 3.0tdi before I settled on the X5. But, you can definitely still tell it's a diesel at idle I won't argue that. But gee it sounds nice when you give it some boot