They block out the noise effective from the wind and the engine and you are in your little world for your self.
What I did not like was that it was a solo thing and that I was too much removed from the surroundings also it was a fiddly thing to remove the helmet and keeping the earbuds in place. After a while one ear kept complaining a bit about the bud inside.
To share my joy of riding with some nice tunes I installed the stereo with 4 speakers (still hunting for the right subwoofer). But above 70 km/h the wind gets too noisy to enjoy this setup much.
I wondered if it was possible to have a nice sound what would work also above 100 km/h and not to be disconnected from the surroundings.
Found a set of nice headphones what were small enough to fit into my helmet and had a good cushion to seal comfortable against my ears without much pressure.
A test before with a set of Maxell headphones proofed futile because of not enough padding and they were not loud enough.
It was a bit of work to get the behind the head plastic removed from the headphones and then it was just a matter of several stripes of double sided foam sticky tape and getting the cable secure between the helmets layers.
I rolled the connection cable to a little loop and fixed it together with the MP3 player on the helmet chin band.