If one is going to ride with earphones, I believe that these are the best available for under-the-helmet use:
http://www.audeoworld.com/
The sound is phenomenal - they have been "Editor's Choice" headphones for many publications. Since the earpiece chassis is vertical instead of protruding out from the ear, it fits flat along the ear and does not come into contact with the inside of the helmet. sing the Comply foam tips, they wil deliver over 25dB of isolation - more than enough to hear the music clearly - but not so much as to drown out all other critical sounds. They are very reasonably priced and they are very long-lasting. The manufacturer, Phonak, is one of the preeminent hearing aid manufacturers in the world; they know something about audionics - and these headphones show it.
Could not recommend these more highly. That said - they probably are illegal* for motorcycle use in several states.
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*STANDARD OBLIGATORY DISCLAIMER:
Any opinion or information set forth above does not constitute legal advice. It is posted for general informational purposes only. No attorney-client relationship is formed by the posting of this material and you have no right to rely on it. I am probably not licensed to practice as an attorney in the jurisdiction where you reside. If these issues affect you - you should seek competent legal counsel in the jurisdiction where you reside. The law varies from jurisdiction to jurisdiction and what is stated here may or may not constitute the law in your jurisdiction.
So there!
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