The Literal Origins of Sounding Board

Beginning during the Renaissance, a flat wooden canopy called a sounding board was placed over church pulpits, amplifying the sound of the preacher's voice, carrying it to the farthest reaches of the church. Similarly, ideas can be spread by a figurative sounding board. A publication, for example, can be a sounding board for propaganda. That's one modern sense of the word. But when sound bounces off a literal sounding board, not only does it reach more people, it also comes across more clearly. Likewise, bouncing ideas off another person can lend clarity to one's thought processes. If someone comes to you and says "How does this sound?" and leaves with his or her mind made up (whether or not you've ventured a word), you have served as a very effective sounding board.