Mouthpiece
WordNet
noun
(1) The aperture of a wind instrument into which the player blows directly
(2) The tube of a pipe or cigarette holder that a smoker holds in the mouth
(3) An acoustic device; the part of a telephone into which a person speaks
(4) (especially boxing) equipment that protects an athlete's mouth
(5) A part that goes over or into the mouth of a person
"The mouthpiece of a respirator"
(6) A spokesperson (as a lawyer)