mega·phone /ˈmɛgəˌfon/
  擴音器
  Meg·a·phone n.  A device to magnify sound, or direct it in a given direction in a greater volume, as a very large funnel used as an ear trumpet or as a speaking trumpet.
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  megaphone
       n : a cone-shaped acoustic device held to the mouth to intensify
           and direct the human voice