Well found part of the answer to my annoyance. There is literally almost scant to no padding under the carpet. Nada, zilch. Just sheet metal then a thin form fitted carpet.
This is what the back looks like eight he seat taken out and carpet lifted up.

 

Padding doesn't necessarily make a car quiet. Ask people who have dynamatted their cars.

 

I beg to differ.. Some dynamat does block high frequency sound & vibration. Then let's say the absence of it definitely doesn't help it either. I suspect thinner sheet metal and combined with scant padding.

 

i think the 3IS and 4GS is pretty quiet inside the cabin. have trouble hearing emergency vehicles until they get very close to me. However, i felt the RX was really loud and bumpy when i had it as a loaner

 

Depends on the specific alloy, of course, but thinner sheet metal can often make a difference.

 

One of the reasons why the RX may be somewhat louder than Lexus sedans is that vehicles of that type, that have a open interior all the way to the rear of the vehicle, tend to amplify road nose coming from the rear wheel wells....the large open space behind the rear seats sometimes acts as an drum or amplifier. That also used to be a problem, decades ago, when there were millions of station wagons on the road. That's not to say that careful and thorough attention to soundproofing won't work in hatchbacks/wagons/SUVs (it certainly does in some of them), but, in general, it is easier to get road noise out of a sedan or coupe with a separate trunk, closed-off rear seats, or other barrier that separates the rest of the cabin inside from the open rear wheel wells.

 

There are multiple threads where people have dynamatted their floorpans and been disappointed with the results on CL. Search for them.

Have you replaced those crappy tires yet?

The better cars are definitely quieter than the entry level cars.

 

Yeah...good point. Tires can make an enormous difference. I've seen them start to howl in as little as 10,000 miles...especially if the alignment isn't perfect and they start to wear unevenly. I'm not sure if this is the tire he has or not, but Bridgestone RE-92 all-season tires used to come standard on many crossover-type vehicles, and, while quite good in the snow for all-seasons, they did tend to drum up road noise as they aged.

 

And he admitted in this thread months ago the car had poor tires on it. Tires are very important on a Lexus.

 

tires are important on ANY vehicle, and are the biggest noise factor these days, with road surface, wind friction, and finally engine as the other major sources.

 

Lol! No not get. But getting REAL close. Went to America tire and they took a measurement with their tire dohiicky thingy and the tread is in the "yellow zone". I suspect two maybe three months tops and these tires will be gone. Man am I happy. Happy, happy, happy. Right up there with the son in law moving out type happy.

 

Well articulated. This is the exact experience I'm annoyed with. So I hammered three layers of Knu noise kollosus (HIGHLY recommend it) sound deadener and three layers of CCC foam. Sitting in the back while my wife drove it did an admirable job of muting the noise coming from the wheel wells. This is without a layer of mass loaded vinyl as I didn't have any on hand but is inbound shortly.
I'm just annoyed that they skimped out on this crusial step in an otherwise a nice SUV in my opinion.
Just to be clear I don't think people realise how noise from inside a vehicle can add stress to you on long commutes. It does without you even knowing it. Now having done the doors and cargo area while installing a stellar sound system I no longer care as much about the commute and have slowed down the mph considerably ( 75 for testing) usually doing 65. Instead of 75-80 to get to my destination to get the hell out of the miserable echo cbamber of a vehicle. It's turning into a wonderful cruiser.

 

Trust me, pick some nice quiet tires and the difference in interior noise will be huge.

 

recommend Michelin Latitude Tour

 

LX still feels old school Lexus quiet with the nice soft comfy ride.
Same goes for the Land Cruiser.