I wake up one morning to the most awful noise I have ever heard. A shrill, scratchy, warbling, pulsating siren whose volume is just on the edge of being painful. I run outside in my bathrobe to try to find the source of the noise, but it is directionless. It seems to be coming from all directions, everywhere.
Standing there on my front lawn, I notice all my neighbors are out as well, many with hands pressed against their ears, some running around franticly like they have mosquitoes trapped in their ear wax. Every dog in the city is howling, adding a thousand dissonant harmonies to the awful noise in the air. I ask a neighbor what it is, and he doesn't know. Spotting a news helicopter overhead, I turn on the local news. The report says that the noise is not just in my town. It's being heard everywhere, all over the world, and its source is still undetermined.
Everyone wears earplugs while we wait for the noise to end, but it doesn't end. Weeks pass and no one can figure out where it's coming from. Scientists are baffled. Unsure what else to do, the Pentagon raises the National Alert level up a few colors. Business and commerce falls into chaos, as no one can communicate clearly over the deafening noise. Houses and businesses are retrofitted with soundproof walls, and this helps, but the noise still gets through. Few can afford the level of soundproofing necessary to totally silence it. Special "Soundproof Cafes" begin popping up everywhere, featuring soothing nature sounds and white-noise to counter the Noise that gets through the ultra-insulated walls.
People begin to develop innovative new ways of communicating. Millions learn sign language. Others constantly wear earphones connected to tiny microphones, which they can swap with whoever they need to talk to. All music concerts but the loudest rock shows become obsolete. For the average working man, there is nowhere on earth he can go where he won't hear the Noise at least as loud as a muted trumpet.
Years pass, and society rearranges itself. Slowly, people adapt. They get used to the Noise. Kids develop street slang for it, like "The Banshee" and "Old Squeaky". Musicians begin writing songs to incorporate the Noise, which most agree is more or less a C sharp. Eventually, there is an entire generation that was born with the Noise, and has never known a world without it. The Noise becomes a part of life.
Fifty years later, the Noise just stops.
Everyone on Earth instantly goes insane.
Society crumbles. Crazed and senseless, mankind stops reproducing. One by one, everyone dies. The human race becomes extinct.
It is now very, very quiet.