Best solution that does it all- hearing protection and great audio - go to
www.protectear.com and look at their products. The plugs, because they are moulded to fit your ear exactly, are extremely comfortable and can be worn for hours.
These are custom made ear plugs that incorporate tiny transducers in line with the ear plugs, connected to a 3.5mm stereo jack that fits iPods, GPS, laptop, or what have you that outputs audio. Worn solely as ear plugs, you get great ambient noise suppression, but not sirens, horns or other things you WANT to hear. You can also listen to the music too, although that will diminish your ability to hear those other extraneous sounds, hence, I never use them for music on the bike, but I do use them for my GPS on the bike.
They are great on long flights too, for deadening the aircraft sound, or watching the movie, or listening to music. Great when you are bunking with a snoring buddy on a road trip too. I've slept with them in all night and never heard a thing.
Be prepared to spend a couple hundred dollars, for the model that comes with the transducers, but they have been worth every penny in my book. Here's a quote from the web site about the "Biker Buddy" product.
"Hearing protection that allows the wearer to hear incoming audio in both ears. It has a 3.5mm stereo jack with separate right and left channels suitable for use with radios equipped with stereo and some monaural jacks. As well, the headset can be used with digital music players (iPod compatible). Designed to be worn with Convertible Y vented earpieces, DualCom can be worn under helmets of all types."
This picture does not show the transducers attached.