sounding-board

n (a) board or canopy placed over a platform, stage, etc to direct the speaker's voice towards the audience, so enabling him to be heard more clearly 增音板（装在讲台、 舞台等上方增加音响洪亮度的板或顶篷）. (b) means of causing an opinion, a plan, etc to be widely heard 宣扬意见、 计画等的手段: The magazine became a sounding-board for its editor's political beliefs. 那杂志成了编辑宣扬其政治主张的传声筒.

soul mate, soul music, soul-destroying, soul-searching, soul-stirring, soulful, soulfully, soulfulness, soulless, soullessly, sound, sound a warning, sound archives, sound barrier (also sonic barrier), sound effect, sound-proof, sound-recording, sound-track, sound-wave, sounding, soundings, soundless, soundlessly, soundly, soundness, sounds, soup, soup-kitchen, soup-plate, soupcon, sour, sour cream, source, sourdough, sourly, sourness, sourpuss, souse, soused, south,