Thanks! So it actually destroys the sound and it has no effect? Or does it have an effect on your hearing, but you don’t perceive it?

Someone believes the active cancelling itself does reduce the music quality due to the fact that there is no earphone able to cancel environment noise 100% perfect.

It always leave some here and affect music quality.

Although I think that is fine enough for me that my main purpose is to block the environment noise.

There is definitely a tradeoff for sound quality and that can be a good reason to disable it in a quiet room. In noiser rooms, it is likely that the background noise is already damaging sound quality more than the ANR will.

As others have mentioned, it might affect sound quality in terms of passing a tiny bit of environmental sound, because ANC isn't 100% efficient. But in terms of hearing, ANC itself has no negative effects on its own, and it is definitely way less damaging to your hearing than if you used the same earphones in the same environment, but without ANC.

You can definitely tell something is going on when the active noise canceling is on but it's not a big deal most of the time. It's good at blocking repetitive noise (office, car, plane) but bad at blocking other things like a car horn, a gun, someone clapping, &c.

How about wind noise?

Depends on how they're set up. My Sony over-ear noise-cancelling set has ambient noise mics that assume a non-windy environment, and thus can pick up wind noise themselves. I turn the noise-cancelling off if I'm going to be somewhere windy, but I have a hunch that putting a little faux fur patch (deadcat) over the ambient noise mic port would fix this.

Actually destroys the sound.

Acoustic equivalent of x + -x = 0.

Based on my knowledge of physics, the wave is eliminated and not in any way perceivable.

I would say it would depend on the position of the microphone, the speed of the electronics and the ability of the speaker to reproduce the negative wave at the microphone.

I don't think it could work perfectly. It would be like putting a beach-ball offshore and using it's motion to move a log closer to shore up and down to cancel all waves hitting a beach.