mouthpiece

/ˈmaʊθˌpis/
noun
  1. The part of a musical instrument, telephone, or other device that is placed in or near the mouth.
    • The phone's mouthpiece was cracked, making it hard to hear the caller.
    • She put the mouthpiece of the scuba regulator into her mouth and took a breath.
    • He cleaned the mouthpiece of his trumpet before the concert.
  2. A person or organization that speaks on behalf of another person or group; a spokesperson.
    • The press secretary acted as the mouthpiece for the president.
    • The newspaper became a mouthpiece for the political party's views.
    • He was seen as the mouthpiece of the student movement.