Do you have a piggy bank? Take an empty piggy bank and put just one little coin in it. Now shake it. It makes a huge racket, right? Clank, clank! Now take a piggy bank that's full all the way to the top, nice and heavy. Shake it. It barely makes any noise. It's quiet because it's full.
The Bible says Wisdom is that treasure. Whoever has a heart full of wisdom is calm, peaceful, and doesn't need to keep shouting "I know! I know!" Wisdom rests in him. Only whoever is "empty" (foolish) needs to make noise to be noticed.