If it is the same thing, mine actually does it in 6th gear
No kidding. It started halfway through my trip to Canada. It is like a "waah waah waah" at 1 second intervals. However, I dropped a couple PSI and went for a "spirited'
ride several weeks ago. It has gone away best I can tell. My assumption is that it actually is the tires. Combined with the engine and drive noise, it just hit that resonant frequency.