You understand you are talking to humans here, right? Actual humans, who perform a lot of actions "on autopilot", without consciously thinking about them, and who may have deeply ingrained habits which are very, very hard to change?
Right, but the problem is, it's unsafe to rely on sound in this manner to begin with, regardless of car noise levels.
Sound can only be used for positive identification - if you can hear a car, it's there. It cannot be used for negative identification - if you can't hear a vehicle, it doesn't mean anything.
This is because there are far too many factors that are at play when it comes to the ability to hear:
- Not every dangerous vehicle makes appreciable sound - an ICE car with its engine off, an EV, a bike, any other small personal transportation device, even a skateboard
- The sound may be masked by another, louder sound
- The sound may seem to come from a different direction, there's no telling how the surrounding environment will reflect the sound around before it's reaches one's ears
- The human crossing may, like you point out, be on autopilot, distracted, or otherwise not perceptive to sound
Because of these, and likely more, factors relying on sound when crossing the street is a horrible idea and will get you killed.
I cannot emphasize this enough, looking both ways when crossing *is mandatory*!
