I forgot to take my sound reducing headphones on this trip, and probably why I have a buzz in my head now.
when I wear those noise cancelling headphones, not only prevents the buzz but makes the car, and primarily the rv,
much more comfortable on long trips. Around town I don't bother. It's the constant rotational road noise, the whine you hear
driving on concrete, that these phones totally dial out. I can listen to my car stereo at same time and hear the music.
I'm sure the highs are muffled but it's very listenable. The Volvo has a good B&O stereo in it and cranked up it is surprisingly
good, for a guy with bad hearing.

I also find them a must while mowing. Not just less noise, the irritating part of it simply eliminated.
pilots have been using this for a long time.
I've tried the 70 dollar ones from Amazon, and for mowing
the lawn they are wonderful. But there really is a difference wearing my Sony or I'm sure a Bose. And my Sony was only a mid level model.
What you want is the good sounds coming
through, not the bad sounds. Involves a number of built in microphones sampling the noise and then it does its electronic voodoo.
I think it's more than just a filter, think it involves some kind of white noise injected to mask the bad noise.
Most importantly, and I've tested this, I can hear sirens just fine. Sirens warble, they aren't steady state noise.
So somehow the electronics figures that out and doesn't suppress it that much. A lot better than hearing a siren though loud rock music
playing. Which I don't listen to...silence can be a real luxury.
time to go fiddle with plants