I was headed home earlier and changed lanes and all of a sudden I heard a loud wind like noise so i checked my dash and saw no engine light go on nor the tire pressure light go on. I parked 5 min. later and checked the tire pressure again and it was fine. Does anyone have experience of this before? I stopped at a stop light. The sound eventually went away then I sped up and the sound came back. Again, this is a 2021 is350 awd. Please help.

Check under the car, maybe picked up some debris or something came loose and is flapping at higher speed. Also check the tires to see if anything stuck to one of them. (I recently had a sudden odd noise, and found a mouse sticky trap stuck to a tire.)

It's interesting that you used the phrase flapping because I had to drop the IS off at the Lexus dealership this morning ( I have the 50000 mile warranty) and I heard this flapping noise as I sped up on the freeway. The other noise was what sounded like a lot of air. They're charging me $95 bucks for the diagnostic but your experience reminds me of my ct200h. I took it in for an oil change at the dealership and they told me mice had been chewing on one of the wires that are used to connect to the dashboard display. I appreciate your response. I will let you know what they say after the diagnostic has been finished.

Lexus told me it was the engine cover that got hit by something thus not honoring the warranty, which was pretty sketchy. I would have heard the noise from something hitting the engine cover. Nevertheless, it had to be fixed so I payed for it and it was repaired this morning in San Diego. I picked up the car in the afternoon and will simply chalk it up as bad luck.

You mean an underbody cover? Engine cover usually means inside the engine bay, which does not make sense unless if it was not put back on correctly.