The illustration below is a sound spectrogram of a 10-minute recording made by Navy ocean-bottom surveillance microphones in the western North Atlantic. The dark vertical streaks in the blue highlighted areas are parts of song from humpback whales; those in the pink regions are calls from minke whales. The dark smudge in the green region is the sound of an undersea earthquake. Such loud natural events are common in many areas of the world's oceans, and appear to have no obvious effect on the calling behavior of whales in their vicinity.

To hear the recording, click on the spectrogram. The sound you will hear is speeded up ten times faster than normal speed, which also raises the pitch of the whale sounds and the rumble of the earthquake by a factor of ten (slightly more than three octaves). The hissing noise that you hear throughout the recording is the natural ocean background noise, which is a result of wind and rain at the surface, as well as distant breaking surf. The humpback song is audible against this background as a series of high-pitched chirps and whistles. The speeded-up minke whale calls sound like very rapid series of clicks, almost like the sounds of insects of frogs. The earthquake produces a loud, low roar, beginning about ten seconds into the speeded-up recording.