Echolocation is a navigation aid that uses sound emissions and their reflection to locate solid obstacles. These signals reflect or 'bounce' back upon encountering a solid object thereby allowing the emission source to navigate around said object. Within the animal kingdom, this mechanism is used by bats to navigate. They emit high-frequency sounds and listen for those sounds to reflect back to them. Cetaceans (members of the whale family) also use the reflection of sounds to navigate. Some blind humans also use echolocation (by using a clicker or making noises themselves) to help navigate within buildings and in areas where there are obstructions. This reflection of sound is also the basic premise behind the use of Sonar (Sound Navigation And Ranging) by seagoing vessels.