I found this discussion enlightening and especially in view of comparison on the engine sound of the LS460 with the LS430. I had a 2005 LS430 with less than 42,000 miles which I purchased a year ago (March 2014). It was the quietest car I have ever owned (and I have owned quite a few Cadillacs over the years). When at idle, I had passengers comment on the quiet....and ask if the engine was still running! The car was stolen in March 2015 and severely wrecked. I was very sad to lose this car. I have replaced it with a 2009 LS460. During the test drive, I did not notice the sound described above, but since then, I have spent some hours in the car (purchased in March, 2015), I have noticed the sound you all have described upon start up and during idling. At first, I was concerned something was wrong with the engine, but the dealer told me that all was well with the car during my last 60,000 mile service. I have come to accept the fact that the LS460 engine is really just different than the LS430 engine. I am very pleased with the performance and handling of this car, which feels like it has more presence and substance (and weight) than the LS430. However, after reading so many comments about engine sounds, I have come to accept that the LS460 engine is more audible under acceleration and idling than my previous LS430. However, once underway, it is serenely quiet and a dream to drive. I personally prefer the LS460 overall.