I'll get right to it. Picture a leather belt hanging out of your window. Now think of the sound it would make while blowing in the wind and slapping the side of your driver door.
That is what i'm hearing when driving over 50-60 mph. The windows are all up. And the sound seems to be coming from the inside of the door.
Any ideas?

 

Are you sure it's inside? Would it be possible to have someone follow you in another car to see if something is flapping in the breeze? I have seen cars with bumpers skins and other stuff like under car spoilers hanging loose. I had an 02 ES that we test drove and didn't buy right away (bought it like three weeks later after we made up our minds but didn't drive it again) that the inner fender was loose for some reason and made a terrible sound when driving. Only found it by going out and pushing and wiggling stuff. Found it loose and tighened it up and all was well.

 

Do you have the body side molding?

 

I do. But they are secure.

 

Check the felt lining in the wheel wells?

 

Checked. Seems intact.
It's a strange noise and I have no idea what it could be. Kinda like a knocking noise.

 

Jeff....take in to lexus !!!!!!!!!! its impossible for someone here in neverland to solve the issue...dont let the bump turn into Mountain...frustration will grow..do the right thg and have it looked at. good luck !

 

Now this is what I should've checked first -- but i'm retarded.
It was the first six inches of the molding. I just got a dent in the door fixed and had them detail the car. They reattached the molding after the body work and of course the noise is now gone.