RCW 46.37.480: Headsets, earphones.

(1) No person shall operate any motor vehicle on a public highway while wearing any headset or earphones connected to any electronic device capable of receiving a radio broadcast or playing a sound recording for the purpose of transmitting a sound to the human auditory senses and which headset or earphones muffle or exclude other sounds. This subsection does not apply to students and instructors participating in a Washington state motorcycle safety program.

(2) This section does not apply to authorized emergency vehicles, motorcyclists wearing a helmet with built-in headsets or earphones as approved by the Washington state patrol, or motorists using hands-free, wireless communications systems, as approved by the equipment section of the Washington state patrol.