There’s no telling whether silence is a real thing or not. It's what your brain creates out of an image. The poems “Silence” 1 and 2 by Billy Collins and “The arrow of a sun” by Henry Wadsworth Longfellow has proven that your mind is thinking out loud by saying that a certain object, or emotion is making a silent sound. Silence is real because there's a point where you don't hear a sound but its not because your brain is always making a sound by thinking. Silence doesn't exist because when it is silent your brain never stops thinking it's always in deep thoughts.
In the poem, “The Sound Of Silence” its stating that silence doesn't make a solitary sound its your brain thinking it is. For example it says, “The silence of falling snow is deafening”.