I think this is a really bad idea unless paired with some regime that penalizes inappropiate use of alarms - and most societies don't treat noise pollution as a real problem. For example, people honk all the time even when there are no safety issues. Or have misconfigured home/car alarms. Outlawing using ANC for blocking "fake alarms" only makes the problem worse.

I don't know… If I'm sitting at home or at a cafe working, I want my headphones to block all bicycle bells and ambulances on the street. Those in traffic could perhaps just turn their ANC off?

We can't even prevent radio advertisers from playing sirens.

as soon they do that all kind of companies will start abusing it, for example the sound of all smart phone notification will use exactly that frequency

Regular alarm sounds already do that, because above 1kHz or so it's the cushioning in the device that does the majority of the cancelling. There's a dip in effectiveness before that because to cancel noise effectively it's best to have a latency lower than a quarter of the wave's period.

Also ANC works best on wide-spectrum sounds, so any kind of siren or the cries of a child will go through, as the spectrum is a series of narrow peaks.

The real safety move is to not put yourself in situations where you're going to collide with the least dangerous class of commuters.

In theory that sounds nice, but I suspect it would be much harder to make work in practice than it seems

However, deaf people are allowed to drive, cycle, walk etc. so sound won't always work anyway.

Ha, I had the same idea before I realized it’ll just be used for ads. It would be cool for pilots’ announcements on a flight, or approaching stations on the train etc. But CVS will use it to tell you to download their app and enroll in ExtraCare Rewards. Or “Did you know you may be due for more than fourteen vaccines all at no cost to you?”

this sounds like an amazing idea, the govt should introduce laws so that the companies do this