It's an issue of noise pollution and, though usually under the radar of the general public, is something that's been studied for decades. Basically, there are three sources of road noise - noise from auto propulsion systems, aerodynamic noise, and tire noise.Now then, about that 69 decibel level.... is there an actual spec somewhere that says that's outside the car??? I mean...who would care unless you're the Green Hornet and buy only silent series tires? I've never seen such a rating on what a car's tires noise puts out to the masses. Maybe that exists, but a decibel level for a given tire inside the vehicle, now that's a real spec someone could use when deciding on what tires to buy because some are certainly louder than others. And then no actual stated weighted measurement level is given.... @ A weighted or C weighted? That's a huge difference between the 2 because C weighted is WITH the bass included whereas A weighted is the LF (low frequency) filtered out for better overall measurements when determining harmful db levels in factories and such for workers long term exposure to factory noises.
Since road noise is mostly LF content, then if the measurement rating is very important if that rating was inside the car. If it was measured at A weighted readings then it would not give a good indication of a car's low frequency management and insulation. C weighted would be MUCH more useful.
Noise from the car's systems dominates idle speeds, and slowly increases as speed increases. EVs create quite a bit less motor noise than ICE vehicles so are quite a bit quieter at very low speeds.
Aerodynamic noise generally does not start getting noticeable till main-road speeds and increases sharply as speed increases from there, so it dominates at highway speed. EVs (generally) are more aerodynamic than similar ICE vehicles, so are a bit quieter at high speeds.
Tire noise, unlike aerodynamic noise, starts at low speeds, and (for ICE cars) generally overtakes engine noise at what are common speeds in residential areas. It is then the dominate source of auto noise till aerodynamic noise starts taking off. For EVs, because they have much less motor noise, tire noise starts dominating quicker.