Safety and Riding with Headphones
It’s common sense and it’s the law:
Bicyclists in New York State are prohibited by law from wearing more than one earphone attached to a telephone, radio or other audio device. § 375(24-a) (NYS VEHICLE and TRAFFIC LAW)
You could be startled by a cyclist passing you, miss a shouted warning about upcoming road hazard. It’s hard to avoid an approaching car you can’t hear.
If that's not enough reason to comply, police can and do ticket for violations.