You may wear earphones in both ears:

To prevent hearing loss caused by exposure to wind and engine noise, you may choose to use ear protection. You may not wear headset coverings, earplugs, or earphones in both ears unless they are specifically designed to reduce harmful noise levels. The headset coverings, earplugs, or earphones must not inhibit the wearer's ability to hear a siren or horn from an emergency vehicle or other motor vehicle.