Often in nature, there are occurrences of abilities found in living organisms which are not found in humans and are thus classified as being outside of our range of capabilities. One such example of this is the natural use of ultrasonic waves whose frequencies exceed those perceived by homo sapiens, being of longer wavelengths, thus being above the audible and visual ranges which are accepted as standards to which all else all relations are compared.

Sound may be expressed an oscillation produced by vibrating objects which may be heard, assuming a proper medium is present to transmit the sound, such as water or air (SPH1). Sound may be addressed in wave form, consisting of wavelengths, the distance a wave travels before the motion begins to repeat, and frequencies, the number of vibrations per second (denoted "f", measured in Hertz, or Hz). Humans are capable of hearing frequencies between 20.0 Hz and 20.0 kiloHz through the use of the cochlea found in the ear and, when sound is measured in decibels (dB), it is observed that humans are able to hear from 0.0 dB, the lower range of hearing, to 160.0 dB, where there occurs the instant perforation of the eardrum in many mammalian species (SPH1). However, several zoological specimens are able to hear sounds beyond homo sapiens and into the ultrasonic range- 16.0 kHz to several billion Hz- some of which may be detected by recording on an audio cassette tape and playing the machine back at a slower speed than was previously recorded, as has been observed with bird calls (Halsey1 225). Such examples of organisms who are able to hear beyond the human sense of hearing include monkeys (limit of 33.0 kHz); cats (limit of 50.0 kHz); mice (limit of 80.0 kHz); dolphins (limit of 150.0 kHz); and bats, who are the only organism known to possess keener hearing than dolphins at 175.0 kHz, or 175,000.0 vibrations per second (Cousteau 169). It is through the use of the ability to hear ultrasound waves which allows for several species to use what is known as "Sound Navigation and Ranging" (SONAR), or echolocation.

Echolation is recognized as a method utilized by a variety of aquatic, nocturnal, and cave-dwelling zoological subjects to localize objects and perceive the environment by means of reflection of ultrasonic sounds, where sound pulses are emitted by the auditory system and reflected from objects in the environment as waves, which may be interpreted by the auditory system, similar to the visual system. The process was termed, "echolocation" by Donald Griffin, who pioneered a breakthrough in studies of the auditory system upon discovering the use of ultrasonics by bats in order to avoid obstacles, although echolocation used by bats was observed in the early 19^th century by Lazzaro Spallanzani, an Italian scientist (I). The use of echolocation provides for an increase in independence from strict use of the visual system, aiding in navigation, orientation, and location of prey in poor light or the dark. Species to use echolocation include bats and dolphins, primarily, but not exclusively, as birds, rodents, insectivores, Megachiroptera, fish, seals, cetaceans, large aquatic mammals, the platypus, and blind humans have been found to use echolocation (I). 

To locate objects in poorly lit or dark environments, users of echolocation may use ultrasonic beams, which are greatly directional. By emitting ultrasound waves in a given direction, the waves reflect off an object in the ultrasound path, which produces an echo effect, sending the waves back to the organism. Through determination of time between emission and receiving of the ultrasound pulse, the distance to the object may be measured and location figured, or, if targeted towards the bottom of a body of water, the depth may be calculated (Halsey5 578). In solid materials, the pulse penetrates the solid without disturbing it and is reflected from the far end, then, through time measurement, the density of the material may be determined (Halsey5 378). The pulse also indicates irregularities of the solid, including holes or flaws. Through the use of what is known as the Doppler Shift, or the shift in frequency produced by a moving source, the speed of the object may be derived as well as the distance: if the reflected signal is Doppler shifted, a change in beat frequency results, where beat frequency is proportional to speed, meaning the greater the frequency, the greater the speed of the object (SPH1). This is particularly useful in locating prey, as in the case of a dolphin, which employs the use of echolocation to catch fish and navigate. ³

When addressing ultrasonic waves, a distinction must be made between the two forms of ultrasound, being low-intensity waves and high-intensity waves. Low-intensity waves are known to pass through a material without disturbing its physical nature, however high-intensity waves are capable of producing chemical and physical changes by generating bubbles, followed by the abrupt collapse in liquid due to high-speed agitation (sonochemistry)(Halsey5 579). Intense ultrasonic pulses may kill bacteria and make significant impacts upon the brain of another organism, or organs found in the body, as dolphins have discovered to be a benefit when catching fish by disorientating the fish and its swim bladder. Cavitation may result in solids due to high-intensity waves, where the particles are subjected to large alternating accelerations which may reach up to 1,000,000.0 g (g denoting gravity in this case). Cavitation in liquids is also possible, where cavities form and collapse violently during compression, with high pressure and high temperature (Halsey5 580).  

In several cases, some organisms live in habitats which may be dark or poor in light, which makes navigation and prey location more complex. However, to overcome the issue, echolocation may be used by emitting an ultrasonic pulse and receiving the reflected pulse from an object, whose distance, density, and speed may be derived. One of the primary species to use echolocation is the dolphin, whose large sensory cells allow for perception of high frequency, each with their own nerve fiber, specially equipped to perceive vibrations in water, similar to other species who depend on hearing as their main sense (Cousteau 168). Hippopotami are able to detect obstacles without emerging from the water, though visibility is less than 30.0 cm (12.0 inches), and even blind homo sapiens have been found to use the echoes from tongue clicks or cane clicks to localize objects and the surroundings (I).