Earplugs worked fine to keep the noise out, but then I had to crank up my helmet speakers almost into distortion to hear the music - because the earplugs not only reduce the noise - they attenuate your music by the same amount. And, on top of that, I have a partial hearing loss already (at least, in part, from riding without hearing protection, when I was young and foolish). Saving what's left of my hearing is priority #1.
So I absolutely never ride without hearing protection, and the foam earplugs are best for that - but I wanted to hear music & phone, too, so......
This is what I finally settled on, and it works totally for me:
I bought these earbuds:
https://www.etymotic.com/consumer/earphones/mk5.html
If you look at their specs, they attenuate outside noise
the same as good foam earplugs. ( > 30db)
They set deep into your ear canal, and don't stick out, so they're comfortable under the helmet . And, since they put the music directly into my ear, I don't have to crank up the volume on my Sena at all, just a comfortable volume - that's not destroying my ears. Audio quality is decent, but not as good as some other (bigger) earbuds.
You can still hear outside sounds (traffic, etc) as well as with the earplugs - if you keep the music to a reasonable volume.
I also wear this helmet liner, which prevents the earbuds from snagging on the helmet - it goes on/off easily with it:
https://cyclecrafts.net/?product=silky-helmet-liner
John Heath, above, recommended the Laminar Lip ....
Absolutely ! - the best $100 I've spent on a farkle. Wouldn't ride without it.