What is the difference between sonar and the doppler effect

Here is an example of a sonar console on a submarine:. As I mentioned earlier, a submarine can use active sonar to tell the speed of another vessel in the water. It does this using the doppler effect. You have probably noticed that as an ambulance or police car drives past you with its siren on, the pitch changes.

This is due to the doppler effect. The pitch of the siren is higher as it moves toward you and lower as it passes and moves away from you. What units are used to measure sound? How are sounds viewed and analyzed? How is hearing measured? What sounds can people hear? What sounds can animals hear? Sounds in the Sea What are common underwater sounds? How does sound in air differ from sound in water?

How do people and animals use sound in the sea? Why do sounds have certain properties? How will ocean acidification affect ocean sound levels? How does marine life affect ocean sound levels? How does shipping affect ocean sound levels? Spherical Spreading Propagation from a sound source array in the near field and far field Wave Front Propagation How does sound travel in shallow water?

How does sound travel in very shallow waters? Use of Sound How do marine animals use sound? Marine Mammal Communication Individual-specific Vocalizations Group-specific Vocalizations Vocalizations Associated with Reproduction Sounds Associated with Aggression Marine fish communication Marine invertebrate communication Marine mammals feeding Marine fish and invertebrates feeding Marine mammal navigation Sound Production How do marine mammals produce sounds?

How do fish produce sounds? How do marine invertebrates produce sounds? Sound Reception How do marine mammals hear? How do aquatic birds hear? How do fish hear?

How do marine invertebrates detect sounds? How did odontocete hearing evolve? How is sound used to measure water depth? How is sound used to find objects on the ocean bottom? Fishing How is sound used to locate fish? How is sound used to identify fish?

The pattern produced by the bug's shaking would be a series of concentric circles as shown in the diagram at the right. These circles would reach the edges of the water puddle at the same frequency. An observer at point A the left edge of the puddle would observe the disturbances to strike the puddle's edge at the same frequency that would be observed by an observer at point B at the right edge of the puddle.

In fact, the frequency at which disturbances reach the edge of the puddle would be the same as the frequency at which the bug produces the disturbances. If the bug produces disturbances at a frequency of 2 per second, then each observer would observe them approaching at a frequency of 2 per second.

Now suppose that our bug is moving to the right across the puddle of water and producing disturbances at the same frequency of 2 disturbances per second. Since the bug is moving towards the right, each consecutive disturbance originates from a position that is closer to observer B and farther from observer A.

Subsequently, each consecutive disturbance has a shorter distance to travel before reaching observer B and thus takes less time to reach observer B. Note that the speed of the source must be less than the speed of sound. An aircraft flying at the speed of sound or greater creates a sonic boom, which is a different effect. See Traveling Faster than Sound for more information.

When the source of sound is moving, the frequency of the sound that you hear is different, depending on your position with respect to the moving source. An important fact concerning this phenomenon is that the speed of sound in air is constant no matter what the speed of the source is. When the source is moving in the same direction as the sound is moving, the source catches up to the previous wave crest, thus shortening the wavelength between crests.

This increases the frequency. When the source is moving away from the direction that the sound is moving, the crests become spread apart. Wavelength and frequency of sound from a moving source change according to your position with respect to the source.

See Doppler Effect for Waveforms for more information.