Although bats, dolphins and some blind folks have used an active sonar (SOund Navigation And Ranging) system for many years (they make little squeaks or clicks and listen for the returning echos) The equivalent mechanical electrical system (ASDIC) was developed in the early years of the 20th century. The system uses both the speed of the returning echo and changes in the frequency of the returning sound to detect location, and direction of the detected object
A passive system (just listening) is used by most animals and birds. Leonardo da vinci proposed a directional listening tube to detect the approach of ships.
In general, only Passive Sonar is primarily used aboard modern submarines due to the noise factor; active pings work both ways for detection much the way tracer bullets do. Passive Sonar can tell you a lot about a target though; bearing (location), type of target (merchant vessel, trawler, warship, submarine, etc.), speed (turncount if it's a surface ship), Angle on the Bow, bearing rate, range (over time after plotting). Active Sonar is only used to verify target range prior to shooting a torpedo.
Passively listening to a target, you can also tell its direction by doppler sound effect, i.e., whether or not it's getting closer or moving away, by volume and frequency pitch. You normally assume that the target is closing on your position; if it wasn't, you wouldn't have detected it.
sonar(sound navigation and ranging)
Sonar. Active and passive
Sonar is when you send sound waves out. They bounce off of objects, letting people know there is an object there. Dolphins and bats, among other animals, use sonar.
SOund Navigation And Ranging. Its used mainly to detect underwater objects.
SONAR stands for SOund Navigation And Ranging.SONAR is a device that uses ultrasonic waves to measure the distance , direction and speed of underwater objects.
The word "sonar" is actually an acronym for "Sound Navigation and Ranging." It is based on the principles of using sound waves to detect and locate objects underwater.
The word "sonar" comes from a combination of "sound" and "navigate" or "ranging." It is an acronym for Sound Navigation And Ranging. Sonar is a technology that uses sound waves to detect objects underwater.
SOund Navigation And Ranging = SONAR Sound is used underwater to bounce off objects. The reflections back can be measured (by electronics) to find our where they are and how far away. Used by submarines, to navigate round obstacles underwater and detect other vessels.
sonar
Active sonar ping is audible, so is not ultrasonic. Passive sonar just listens, but it takes time to determine objects bearing, speed & direction of travel. There is ultrasonic sonar for short range detection such as mines and frogman.
It maps ocean-floor features, sea beam relies on sonar which is the use of sound waves to detect & measure objects underwater.
1. A system using transmitted and reflected underwater sound waves to detect and locate submerged objects or measure the distance to the floor of a body of water.2. An apparatus, as one in a submarine, using sonar.3. Echolocation.http://www.thefreedictionary.com/sonar