Most volcanoes rumble before they erupt, but not Alaska's Mount Redoubt, which let out a primal scream before it blew its top in 2009. Preceding the big blow were little earthquakes that began to accelerate, one after another, like a drumbeat building to a climax. Here's a 10-second clip of what the volcano's primal scream sounded like, courtesy of the University of Washington:
The seismic waves are generally too slow to hear, but they can be sped up into the audible range.
