Eh?
Somebody had to say it.
This is a very personal thing. The concept that's worked for me is the same one the previously mentioned plugphones use: An earbud that fits completely inside your ear canal, thereby providing both noise isolation and access to music at a reasonably low volume.
I've tried 'em and they're good.
However, because of my particular anatomy (my ears aren't that large) the protruding part of the plugphones gets pressed on by the helmet and makes them a bit uncomfortable for me.
What I use and highly recommend is the PlugUp S-plugs. These fit ENTIRELY in your ear canal so the only thing that sticks out is the wire. They give noise isolation easily as good as regular earplugs, which means I don't need to crank up the audio volume at all.
They are absolutely awesome and I won't ride on the street without 'em. I listen to podcasts/NPR instead of music, but that's just personal preference. It's easier to get distracted and lost in music for me, and that's a bad thing when riding.
The S-Plugs are relatively expensive for standard earbuds but they work so well that for me, they're worth it.
So bottom line: Same concept as plugphones but different execution. The plugphones are cheap enough to take a risk on but if they don't work, you won't regret investing in the S-plugs.
https://www.plugup.com/best_and_most...22-3.5-4.5.htm