Dolphin Echolocation (Sonar)

Introduction

Echolocation is the production of sounds by certain animals and use of the echoes the sounds produce for detecting obstacles in the animals' paths and perhaps for locating food. The term echolocation was coined (1944) by Donald R. Griffin to describe this process. Echolocators include many bats, porpoises, some whales, several species of birds, and some shrews. Blind people, as well as animals that live where lighting is unpredictable, also use a form of echolocation. Thus, the dolphin echolocation is the ability of dolphins to locate and identify important aspects of their environment, particularly conspecific or prey. It is based on the propagation of acoustic waves in the water, on the principle of active sonar. While, the term Sonar (an acronym for sound navigation and ranging) is a technique that uses the propagation of sound underwater (primarily) to navigate, communicate or detect other vessels (shown in Figure 1). The sonar can be used as a means of acoustic location, operating similarly to GPS IBZ type. In fact, the acoustic location in the air was used before the GPS, while still implementing the SODAR (aerial vertical scan sonar) for Atmospheric Research. The sonar is an American term dating from World War II (A parallel system, radar, uses radio waves to locate objects in the air). Most of the advances made in sonar technology since World War II have been military applications. Sonar systems are used to hunt submarines, to control antisubmarine weapons, to direct homing torpedoes, and to locate mines. Civilian sonar systems called echo sounders are used by both commercial and sport anglers. Marine seismologists employ sonar that generates sound by means of a small explosion (Thomas, pp. 24).

In our study, the whales with tiny teeth are called dolphins. We call them mammals from the order of Cetacea and of the families, Grampidae, Delphinidae, and Platanistidae, and they include about the number of fifty species. They all have the teeth beaklike snout and are sharp. Most of the species are meant been attributed by the term porpoise, but porpoises are members of Phocaenidae family. And the other dolphin like mahi mahi and dardo do not come under the umbrella of this type and are supposed to be the sport fish (Suga,pp.63).

The use of sonar by dolphins, much older and sophisticated than its human use is not a coincidence. Long before the industrial developments of the 20th century, the constraints of the aquatic environment have led mammals to use localization methods that are effective underwater. Even if it is possible to use for shallow (few meters) during the day, the absence of light (turbidity , depth, poor lighting outside) makes sense very quickly ineffective. In contrast, the sonar is still operational and can locate prey and obstacles to vast distances (several hundred meters lower frequencies ). In addition, acoustic waves do not propagate only in water, but can also traverse denser materials, thus offering the possibility to find fish hiding under the sand or in the algae. Finally, the sonar ...