What is Infrasound Communication?

        Elephants are capable of producing calls with sound frequencies of 5 Hz (hertz) to 9,000 Hz [5].  These calls take the form of rumbles, snorts, screams, barks, and other calls.  The lowest frequency calls are called "rumbles", which often include infrasound signals [5].  In elephants, the minimum frequency of a male's rumble averages at around 12 Hz (3 octaves lower than a man's voice), while the minimum frequency of a female's rumble is about 13 Hz and a calf's is around 22 Hz [5].  In human speech, a man's voice usually ranges about 3 octaves higher (around 110 Hz) than the rumble sounds of a bull elephant [5].

Hear an ultrasound elephant call here.

         Acoustic communication (as with chemical signalling) can give short- or long-distance information. Acoustic communication is omni-directional, short-lived, and difficult to localize.

         Acoustic signals that use air as a substrate are subject to possible degradation by the environment through reflection, refraction, and absorption.

        Infrasound communication is a type of auditory communication that is better-suited for long-distance communication in that its' substrate is the ground, and so it is not subject to  sound degradation caused by air (for example, temperature can affect the way sound travels). The low-frequency signals of infrasound can also give directional and distance information of the caller relative to the receiver when the infrasound signals have accompanying higher-frequency harmonics [1].

© Georgia Kirkpatrick and Lacy Lackey 2006