Echolocation
Homework
Name:
____________________ Group: ______
Watch this movie
about a person who uses echolocation:
https://www.youtube.com/watch?v=r9mvRRwu5Gw
1.
Why does this person use echolocation?
2.
What is the range that this person is capable
of?
3.
Do you think you could learn how to do the
same thing?
4.
Do
you think this the only person in the world who can do this or can anyone learm?
Watch
this video:
https://www.youtube.com/watch?v=xATIyq3uZM4
This
section adapted from Discovery of Sounds In The Sea http://www.DOSITS.org
Look at Sound sim – http://phet.colorado.edu.
Choose interference by reflection, choose Pulse.
1.
Send
one pulse at a time. What do the waves do when they hit the barrier?
SONAR SOund Navigation and
Ranging. Uses this idea of sound bouncing back. Scientists know how fast sound travels in
water. They send out a sound and then wait for it to come back. The time it takes to come back tells them how
far away objects are.
Of
course they need to send lots of sounds in very specific directions and then
they can tell not only how far away but where and how big the objects are.
Bat, Dolphin and
Whale communications
Watch the video
http://www.dosits.org/galleries/audio/marinemammals/baleenwhales/humpbackwhale/
scroll down to the
“Underwater video of humpback whales” off the coast of Hawaii.
2.
Can
you see or hear the whales easier? (explain)
Background
Information (read all of this before
moving on):
Dolphins and
porpoises are the smallest toothed whales. Including orcas and pilot whales,
there are 32 species of oceanic dolphins, 5 species of river dolphins, and 6 species
of porpoises. Bottlenose dolphins, like Flipper the TV star, are the most
familiar. While humans rely primarily on sight to perceive their environment,
scientists all agree that dolphins communicate with one another by using sounds
and body language.
Clicks and
whistles are the two main types of dolphin vocalization. Each individual
dolphin has its own "signature whistle", which is a series of
whistles, like a dolphin Morse code, which is distinct from any other member of
the group. This signature whistle provides a way for dolphins to recognize and
bond with others.
Some dolphins
use echolocation
to help them find and capture food.
The
term echolocation refers to an ability that enables bats, dolphins and
whales to essentially "see" with their ears by listening for echoes. They echolocate by producing clicking sounds and then receiving and
interpreting the resulting echo. Echolocation is Nature’s Sonar.
Dolphins produce directional clicks in trains. Each click lasts about 50 to 128 microseconds.
The click trains pass through the melon (the rounded region of a dolphin's forehead), which consists of lipids (fats). The melon acts as an acoustical lens to focus these sound waves into a beam, which is projected forward into water in front of the animal.
Sound waves travel through water at a speed of about 1.5 km/sec (0.9 mi/sec), which is 4.5 times faster than sound traveling through air. These sound waves bounce off objects in the water and return to the dolphin in the form of an echo.
High
frequency sounds don't travel far in water. Low frequency sounds travel farther
because of their longer wavelength and greater energy. Echolocation is most
effective at close to intermediate range because dolphins and whales use high
frequency sounds. Their range is about 5-200
meters for targets 5-15 centimeters in length. In
other words, some dolphins can use echolocation to detect a 15 centimeter (6
inch) long fish a football field away!
The major areas of sound reception are the fat-filled cavities of the lower jaw bones. Sounds are received and conducted through the lower jaw to the middle ear, inner ear, and then to hearing centers in the brain via the auditory nerve.
The brain receives the sound waves in the form of nerve impulses, which relay the messages of sound and enable the dolphin to interpret the sound's meaning.
By this complex system of echolocation, dolphins and whales can determine size, shape, speed, distance, direction, and even some of the internal structure of objects in the water.
Bottlenose dolphins
are able to learn and later recognize the echo signatures returned by preferred
prey species.
Despite the effectiveness of echolocation, studies show that a visually-deprived dolphin takes more time to echolocate on an object than a dolphin using vision in tandem with echolocation.
Go to the audio gallery again and jump to topic “common dolphin” which is a toothed whale. Listen to the two sound clips of the dolphins. http://www.dosits.org/galleries/audio/marinemammals/toothedwhales/commondolphin/
3. Describe what you hear in both cases. What is different about the sounds in each case?
Read the description below the two sound clips about common dolphins.
Dolphins produce non-verbal
sounds by slapping a body part against the surface of the
water, which makes
both a sound and a splash. Tail or fluke slapping is also common.
Kerplunks are another
non-vocal sound made by the tail. Other parts of the body used
to produce noise
in a slapping manner are pectoral fins and the whole body. Finally, jaw
claps are made either
above or underwater.