Songfacts®:

• Written by Dream Theater bassist John Myung and guitarist John Petrucci, the song title stands for "signal-to-noise," a technical term to describe the quality of a transmission (the "signal-to-noise ratio") that is often used as a metaphor for the value of what enters our consciousness.
  
  Petrucci told Your Majesty, Dream Theater's official French fan club, that the song came from "a very spiritual John Myung observation" about how we are sinking under all the bad news about war, natural disasters and drug abuse. He explained:
  
  "The signal represents yourself and your clarity and how you resonate in a way that is pure, and the noise represents all of the negativity in the world - all the constant bombarding of bad news and negative headlines and famine and drug epidemics and earthquakes and hurricanes and all the distractions [like] cameras and cell phones and news. Take it all away. That represents the noise. The whole idea in the audio world is you want the signal-to-noise ratio to be such that the noise is really low and that the sound is really clear. He used that as a spiritual metaphor to push the noise down, so you can find your [zen]."
• About four minutes into the track there's a sample of someone saying "wow." The general consensus among Dream theater fans is that the voice belongs to the actor Owen Wilson. Petrucci told Ultimate-Guitar he didn't know anything about it. "Maybe he visited the studio or something."
  
  Dream Theater do have history with Owen Wilson. In 2005's "Octavarium" there is the line:
  
  Jack the ripper owens wilson phillips and my supper's ready