The audio file above is a time compressed harmonic tremor from Mt. Erebus. The signal representation above, called a "sonogram" or "spectrogram", shows the evolving spectral content of the audo signal as a function of time. The tremor was recorded on February 3, 2001. The audio is a vertical seismogram, with a sampling rate of 40 samples per second, sped up 100 times to transpose the very slow seismic frequencies into the audible frequency band. Thus, the true data length is 1 hour but ths sound file is compressed to less than 1 minute. The sound file is rather trombone-like in character.