Infrasound

The Earth really is a living thing in many senses of the word. For instance, it is very active – it even makes sounds.

Q:
Hi, Wondering what kind of sounds the inner earth makes? Do you know where I might go to hear this?
Thank you 
-Nathan W.

A:
There are sounds from the "inner Earth", but they are generally at frequencies below what the human ear can detect - this frequency range is called "infrasonic". Occasionally these can be heard, but not normally.

I once heard a recording from a seismometer located on Tungurahua volcano in Ecuador - but it had been electronically speeded up about 400 times to bring the signal up into the audible range. It sounded like a large animal moaning and roaring. This of course would be normally inaudible to the human ear.

Here is one somewhat different, for volcanic gas venting: http://volcano.oregonstate.edu/vwdocs/videos/siocomm.mov 

Here is an example of the sounds of an actual surface eruption at Tungurahua: http://en.rian.ru/video/20101202/161596301.html

Note that if the volcano is not actually erupting at the surface, the sounds made are almost always inaudible (infrasonic).

More volcano sounds can be heard here: http://volcano.oregonstate.edu/book/export/html/385

In some volcanoes there is a seismic signal detected called "harmonic tremor" - it is generally thought to be caused by fluid movement through conduits deep below the volcano, and sometimes is a portent of an impending eruption (Mt Pinatubo in the Philippines in 1992, for instance). Harmonic tremor is typically in the 2 Hz frequency range - well below the lowest frequency that a human ear can detect (which is about 20 Hz).

Earthquakes (shifting, sliding crustal plates) also generate seismic waves, but like those under a volcano they tend to be mostly at frequencies well below what a human ear can readily detect.

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