You may wear earphones in both ears:

Question

To prevent hearing loss caused by exposure to wind and engine noise, you may choose to use ear protection. The headset coverings, earplugs, or earphones must not inhibit your ability to hear a siren or horn from an emergency vehicle or other motor vehicle.

Accepted Answer

If they are designed to block harmful noise levels.

Answer

If you are listening to your favorite music.

Answer

To dampen the sounds of horns and sirens.

Answer

For any reason.