Bioacoustics, the study of living sound
Bioacoustics is a branch of science concerned with the production of sound and its effects on living systems. In particular, animal communication, deals with the production, meanings (animal linguistics and cognition), and effects of sounds generated by animals. There are different ways animals communicate, including scent (pheramones) and by body language. However the most effective type of communication for most species is sound.
There are many specializations of animal communication and bioacoustics, the most popular being the studies of bird song. Please go to the LINKS if you are interested in bird song.
There are several ways to analyze sound, however each vocalization, whether it comes from a human or an elephant will be described by in frequency and amplitude, and time.
The frequency of a sound or vocalization is the pitch. In other words a human child's voice will probably be higher than a human adult. Frequency level is expressed in Hertz or Hz.
Infrasounds are sounds below the human range of hearing, technically 20Hz, but most adults will be hard pressed to hear anything below 40 Hz. Your average sub-woofer speaker goes down only to 25-40 Hz. However, at high enough amplitude (very loud) you can feel infrasound, it will shake you. Anyone that has ever watched the space shuttle take off will tell you that it shook the ground and rattled windows, that is infrasound! Infrasound is a long, sound wave. It can pass through forests, buildings and even mountains. For example, the space shuttle taking off creates a very loud sound pressure wave of .02Hz (very, very low). It takes @20 minutes for this sound to reach Langley Air Force Base in Virginia, from Kennedy in Florida. This sound wave will pass through everything on its way, and will continue around the earth until it finally dissipates due to attenuation (lessening of the amplitude of the signal over distance/time). Animals that generate infrasound include elephants, whales, alligators, hippos, rhinos, giraffe, lions, okapi, tigers and several birds. The common thought used to be that only large animals could generate infrasounds, we now know that smaller animals do produce infrasound and there are probably many more we do not know of. Fauna Communications specializes in studying this type of sound.
B:) Sonic range
Sonic sounds are within the range of human hearing, technically 20 to 20,000 Hz. More likely for adults it is between 40 to 15,000 Hz. Many animals communicate in the sonic range, most mammals, birds, fish, etc.
Ultrasounds are sounds that occur above the range of human hearing, or above 20,000 Hz. Animals that communicate in this include Dolphins, bats, many birds and insects. Ultrasounds are short sound waves that bounce off trees, rocks, etc. This is why bats and dolphin use theses signals for echolocation, they actually see by how the sound bounces back to them. This is a fascinating area of sound production, and also one which Fauna Communications is interested in.
The amplitude of a sound or vocalization is its loudness. A human whisper will be lower in amplitude than normal human conversation. Amplitude is normally expressed in decibel level or dB. A plane taking off will be higher in dB than clapping your hands. A rock concert usually has amplitudes above 120 dB, where 130 is the threshold for pain. 120 dB is too loud. If you do not use ear protection at a rock concert, you are damaging your ears. Once damaged, your hearing will never be the same. Many rock musicians are deaf because of this.
Amplitudes from 40-70 are considered normal for human conversation, but many animals use sounds that are louder or quieter. An elephant produces a sound at 14Hz (infrasound), we cannot hear it but we can feel it because the amplitude is 90dB, it is loud. A giraffe produces a sound at 14Hz, and we cannot hear it or feel it because the amplitude is 40dB, it is quiet.
There is much much more to animal communication, that is simply not possible to write about here. For more information please see the LINKS page.