Setting the Scene

Using echoes

Setting the scene

Echoes are reflections of sound waves. You will have come across different examples of this in everyday life and may not have realised it. In this activity you will learn about the usefulness of echoes.

Aims

In this activity you will:

§ learn what ultrasound is

§ describe and explain uses of echoes and ultrasound.

You will be working scientifically to:

§ present reasoned explanations.

Task

Read the text and answer the questions that follow.

If you walk into a large empty hall with stone walls and floors you may hear your footsteps echoing. Echoes are the sound reflections from hard surfaces. In a very large room, the echo is quiet and takes a long time to be heard.

Some animals use echoes to work out where nearby objects are, for example, at night or underwater. The animal sends out a signal, listens for its echo, and works out where the object is. This is called ‘echolocation’. Echolocation works well underwater as sound travels quicker underwater than in air.

Many animals using echolocation produce ultrasound signals. ‘Ultrasound’ is sound that is too high for human hearing. The signals travel as a focused beam giving a lot of detail about nearby objects.

Dolphins make very high-pitched clicks using their nasal sacs. The clicks reflect from nearby objects. The dolphin detects echoes using its ears and can work out the distance to the object and what it is made from. By turning its head, the dolphin can also work out the direction and size of the object.

Questions

1 State the meaning of echolocation.

2 After the animal sends out a signal, describe the next two stages in echolocation.

3 Explain why echolocation is more effective in water than in air.

4 Explain why many animals use ultrasound, rather than audible sound, for
echolocation.

5 Try this short experiment with a partner. One of you closes your eyes. The other person clicks their fingers near your head, for example, behind your head or to one side. Change the distance and position of the clicks. Work out where the sound is coming from.

6 Use your experiment to describe how dolphins tell which direction the object is in and how far away the object is

Extension

1 Bats live in large colonies in caves and buildings. At night they hunt for flying
insects. Explain how a bat uses echolocation to hunt, find out where they are, and
avoid collisions with other bats.

2 Different species of bats use different sounds for echolocation. Bat detectors are machines that are used to identify different species of bats. Explain how a bat
detector can tell which type of bat is flying.

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