Control boxes for headphones; covers for headphones; headphones; headphones for audio apparatus; headphones for microphones; stereo headphones; two-way plugs for headphones; plug adapters for headphones; stereophonic apparatus incorporating headphones for personal use; earphones; earphones for recording apparatus; earphones for radios; apparatus for use in audiovisual communication; audio amplifiers; audio and video receivers; audio cable; audio cable connectors; audio electronic instruments; audio equipment; audio frequency apparatus; audio players; audio processing apparatus; audio speakers; wearable activity trackers; signal processes for audio speakers