Imagine the scene: you and a group of friends – concerned about the ever-increasing level of surveillance of, and spying on, the public by agencies of government, the intelligence community, and the military – decide to head off to a local, peaceful demonstration that is being held in your hometown. In total, a couple of hundred people are there to voice their concerns that way too much control is being exerted upon the population. Suddenly, however, things go distinctly awry. No, we are not talking about the police turning up with water-cannons or Tasers. We are talking about something much worse and far more disturbing. In no time at all, everyone in the crowd suddenly feels nauseous. Some lose their balance and fall over. Others vomit. More than a few are overwhelmed by dizziness and have to lay on the ground. Some develop the shakes. None of this is due to the hot weather or hysteria. Quite the opposite: you have been targeted, and hit by, a weapon that has disabled you via nothing less than sound. Although it is something we give little specific thought to, there is no doubt that sound plays a massive role in our lives and from varying perspectives. The sound of the voice of an old friend we haven’t seen in years can make us happy. The screams of someone late at night provoke concern and worry. The sirens of fire trucks might provoke anxiety. And music can be uplifting, relaxing, or energizing, depending on the type of music one prefers. There is, however, another aspect to sound: it can be used as a weapon against us; a weapon of control. But, before we get back to the issue of control, an important question needs to be asked: what, exactly, is sound?