Noise Cancelling Teslas!
Teslas are really quiet but road noise is kind of loud. Especially on the highway. Using its awesome speakers, and microphones, if Teslas could produce a sound wave inside, that is opposite to the road noise, It would make the cabin much quieter. Hopefully, this could be implemented over the air. But I'm not too sure about the microphones, because they have to be outside the vehicle. Emergency sirens and honks will not be cancelled, because quick changes in the sound waves always come through, they can't be cancelled that quickly.
The Bose 700 headphones use its external microphones to listen to its surrounding noise, and phase-invert it by 180 degrees to reduce unwanted noise. And it's doing a great job. Specifically, when surrounding noise is at a constant frequency, like road-noise, it's doing a phenomenal job.