What is Echolocation Answer Key

Nature’s own sonar system, echolocation occurs when an animal emits a sound wave that bounces off an object, returning an echo that provides information about the object’s distance and size.

Over a thousand species echolocate, including most bats, all toothed whales, and small mammals. Many are nocturnal, burrowing, and ocean-dwelling animals that rely on echolocation to find food in an environment with little to no light. Animals have several methods for echolocation, from vibrating their throats to flapping their wings.

Nocturnal oilbirds and some swiftlets, some of which hunt in dark cave environments, “produce short clicks with their syrinx, the vocal organ of birds,” Kate Allen, a postdoctoral fellow in the Department of Psychological and Brain Studies at John Hopkins University, says by email.

Some people can also echolocate by clicking their tongues, a behavior shared by only a few other animals, including tenrecs, a shrew-like animal from Madagascar, and the Vietnamese pygmy dormouse, which is effectively blind.

Bat signals

Bats are the ultimate poster animal for echolocation, using their built-in sonar to pursue fast-flying prey at night.

Most bats, such as the tiny Daubenton’s bat, contract their larynx muscles to make sounds above the range of human hearing—the batty equivalent of a shout, Allen says. (Related: When it comes to echolocation, some bats just wing it.)

Bat calls vary wildly among species, allowing them to distinguish their voices among other bats in the neighborhood. Their calls are also specific to a particular environment and prey type: The European bat “whispers” in the presence of moths to avoid detection.

Some moths, though, have evolved their own defenses against echolocating bats. The tiger moth flexes the tymbal organ on either side of its thorax to produce clicks, which jams bat sonar and keeps the predators at bay.

As expert echolocators, some bats can zero in on objects as small as 0.007 inch, about the width of a human hair. Because insects are always on the move, bats have to click continuously, sometimes making 190 calls a second. Even with such difficult quarry, the predators can still eat half their weight in insects each night.

Leaf-nosed bats make echolocation calls through their large, intricately folded noses, which helps focus sounds that bounces back. Some species can also rapidly change their ear shape to accurately pick up incoming signals.

A few fruit bats, such as the South Asian lesser dawn bat, even make clicks by flapping their wings, a recent discovery.

Watch a bat use echolocation in total darkness

A slow-motion video shows a Macroglossus fruit bat zero in on a perch during an experiment.

Ocean soundwaves

Echolocation is a logical strategy in the ocean, where sound travels five times faster than in air.

Dolphins and other toothed whales, such as the beluga, echolocate via a specialized organ called the dorsal bursae, which sits at the top of their head, close to the blowhole. (Read how whales have a “sonar beam” for targeting prey.)

A fat deposit in this area, called the melon, decreases impedance, or resistance to soundwaves, between the dolphin’s body and the water, making the sound clearer, says Wu-Jung Lee, a senior oceanographer at the University of Washington Applied Physics Laboratory.

Another fat deposit, stretching from a whale’s lower jaw up to its ear, clarifies the echo that returns from prey, such as fish or squid.

Harbor porpoises, a favorite prey of orcas, make extremely speedy, high-frequency echolocation clicks that their predators can’t hear, allowing them to remain incognito.

Most marine mammal echolocation sounds are too high for humans to hear, with the exception of sperm whales, orcas, and some dolphin species, Lee adds.

Navigating by sound

In addition to hunting or self-defense, some animals echolocate to navigate through their habitats.

For instance, big brown bats, which are widespread throughout the Americas, use their sonar to weave their way through noisy environments, such as forests abuzz with other animal calls.

Amazon river dolphins may also echolocate to move around tree branches and other obstacles created by seasonal flooding, Lee says.

Most humans who echolocate are blind or vision-impaired and use the skill to go about their daily activities. Some make clicks, either with their tongues or an object, like a cane, and then navigate via the resulting echo. Brain scans of echolocating humans show the part of the brain that processes vision is employed during this process. (Read how blind people use sonar.)

“Brains don’t like undeveloped real estate,” Allen says, so “it’s too metabolically expensive to maintain” echolocation in people who don’t need it.

Even so, humans are remarkably adaptable, and research shows that, with patience, we can teach ourselves to echolocate.

Have you ever heard that bats use echolocation to understand their surroundings? Since they are generally nocturnal with poor vision, they use sound in order to probe their environment, making them a deadly night-time predator. But how is this possible? In this article, we will discuss the meaning of echolocation, how it works, where it is used, and we will cover some examples.

Meaning of echolocation

The meaning of echolocation is already in the word itself.

Echolocation is the use of echoes, i.e. reflected sound, to locate objects.

How echolocation works

The basic principles behind echolocation are the constant nature of the speed of sound through a given medium (another word for material) and the fact that sound waves partially get reflected off of interfaces (another word for boundary surfaces) between different mediums. The idea is to produce a sound travelling in a particular direction, wait until you hear its echo, and then calculate the distance the sound has travelled. This can be done using the equation of constant motion:

,

or, in symbolic form,

,

whereis the distance the sound has travelled in metres,is the speed of sound through the medium that the sound is travelling through in metres per second, andis the time between producing the sound and hearing its echo in seconds. The distanceto the object that the sound reflected off is given by, because the sound will have travelled twice that distance once you hear the echo:

.

See the figure below for a schematic representation of echolocation.

You are in an empty and quiet space, and there is a big wall facing you. You want to know how far away it is, so you clap your hands and record the time that passes until you hear an echo. You see that it took. You conveniently know the speed of sound in air to be, so you calculate the distanceto the wall as follows:

.

You conclude that the wall isaway from you.

This is not the only information that can be gathered from an echo. In addition, by employing knowledge of the Doppler effect, the frequency of the echo compared to the frequency of the original sound gives information about the velocity of the object. Furthermore, the loudness of the echo (the amplitude of the sound wave) can be used to gather information about the reflection of the sound wave, which is influenced heavily by the density of the object. Therefore, the density of the detected object can also be determined. Lastly, if you can determine the direction of objects (see below for how animals do this), then you can also determine the size of objects by seeing in which directions the object is present (bear in mind that you already know how far away the object is, so some simple trigonometry will give you a size).

Uses of echolocation

Echolocation is used by animals and ships, but it is also used in medicine. One part of a ship's use of sonar is the use of echolocation. A ship can send an ultrasonic sound wave (i.e. of a frequency higher than, outside the range of human hearing) through the water, and detect its echo. This way, it can map objects that are around the ship as well as the seabed, and it uses this information to navigate.

In medicine, an ultrasound scan can be used to look at an unborn baby. For this, we use equipment that emits ultrasound waves and can also detect them. The soundwaves will reflect off of tissue boundaries, so the equipment can form a 3-dimensional image of where all the tissue boundaries are. This way, it can construct a complete image of the baby inside the womb. This is also a form of echolocation. See the article on applications of ultrasound for more information on the use of echolocation by ships and in the medical field.

Some animals that use echolocation are bats, some birds, whales, some shrews, and even some blind people. Using echolocation means that you don't have to rely on your eyesight to navigate. For all animals, this is useful during the night-time. For animals that live underwater, this is also useful during the daytime, because light does not travel very far through water, while sound does. Thus, whales are able to "see" a lot further using echolocation than using their eyes, which is highly beneficial in the vast oceans.

In general, the sounds produced by animals for echolocation are very loud so that they can perceive objects that are far away, and very high-frequency (mostly ultrasonic) because high pitches give information with better resolution (this can be compared to lightwave resolution and the use of scanning electron microscopes).

All echolocation is based on the same principle. One could choose to differentiate between biological and technological echolocation and call them different types. One could also choose to differentiate between what medium is used for the sound to travel through, which would categorise bats (air) and whales (water) into using different echolocation types. There is also a big difference in how animals determine the position of objects.

Dolphins have a special organ that concentrates their sound into a beam travelling in a particular direction. If an echo is heard, this must come from an object in that direction. Dolphins can 'scan' a whole animal by producing sound beams in multiple directions, and are able to tell different animal species apart via this method.

Alternatively, bats emit sound in all directions (they effectively just scream), but they use the fact that they have two ears to determine the direction that an echo is coming from, and the difference in timing and loudness that both ears perceive gives the bats the information they need. For example, if the right ear hears the echo before the left ear, then the echo must come from the right, so the object must be to the right. This is also how humans can interpret the direction of a sound.

Examples of echolocation

For these examples, assume that the speed of sound is aboutthrough water and aboutthrough air.

A dolphin produces a short sound burst of, and aftershe hears an echo. How far away is the object that the dolphin just perceived?

Answer: The dolphin lives underwater, so sound will travel at the speed of sound in water,. We calculate the distancefrom the dolphin to the object by using the formula relating the travel distanceof the sound, the echo time, and the speed of sound in the medium:

.

We conclude that the perceived object isaway from the dolphin.

A bat produces a screech and afterhe hears an echo. His left ear picks up the sound earlier than his right ear. How far away is the perceived object from the bat and what direction is it in?

Answer: The sound from the echo is coming from the left, so the object is to the left of the bat. The bat is on land or flying in the air, so the sound will travel through the air. We calculate:

.

We conclude that the perceived object isaway from the bat.

Echolocation - Key takeaways

• Echolocation is the use of echoes, i.e. reflected sound, to locate objects.
• Ifis the speed of sound in the correct medium andis the time between producing the sound and hearing the echo, then the distanceto the perceived object is given by .
• Echolocation can also provide information about the velocity, density, and size of an object.
• Animals and ships use echolocation to map their surroundings. It is an alternative to eyesight.
• The sounds produced for echolocation are generally loud and ultrasonic.
• There is no standard differentiation of echolocation into types, but there are differences in how animals use echolocation.
• Make sure to use the correct speed of sound in your calculations.