资料来源 : Webster's Revised Unabridged Dictionary (1913)

Speaking \Speak"ing\, a.
   1. Uttering speech; used for conveying speech; as, man is a
      speaking animal; a speaking tube.

   2. Seeming to be capable of speech; hence, lifelike; as, a
      speaking likeness.

   {A speaking acquaintance}, a slight acquaintance with a
      person, or one which merely permits the exchange of
      salutations and remarks on indifferent subjects.

   {Speaking trumpet}, an instrument somewhat resembling a
      trumpet, by which the sound of the human voice may be so
      intensified as to be conveyed to a great distance.

   {Speaking tube}, a tube for conveying speech, especially from
      one room to another at a distance.

   {To be on speaking terms}, to be slightly acquainted.

资料来源 : WordNet®

speaking tube
     n : a tube for conveying the sound of a voice from one room to
         another