Whenever a wave strikes a reflective surface the energy rebounds. ie the wave is reflected.

Think about water waves reflecting off the hard surface at the side of swimming pools.

The angle that the incoming wave makes with the surface is always the same as the angle that the outgoing wave makes with the surface.

This is the same as when you play pool or snooker. When a ball hits a cushion it always bounces out at the same angle as it hits.

Sound waves reflect in this way. For a surface to reflect sound well it is usually smooth and hard. eg a brick wall.

Question 1. Compare sounds that you might hear in a room with bare floors, walls and windows to a room that has carpets, soft furniture and curtains.

The way a space ‘sounds’ due to how it reflects or absorbs sound is called the acoustics of that space.

If a reflected sound arrives at your ear less than 1/10 second after the original sound then your brain hears both the original and reflected sound as one sound.

If the reflected sound arrives at your ear more than 1/10 second after the original, your brain will hear both sounds separately. You hear an echo.

Question 2. If sound is travelling through air at a speed of 340ms-1, then how far will it travel in 1/10 second?

Question 2.

Speed = 340 ms-1

Time = 1/10 s

Distance = ?

Question 3. How far from a reflective sound surface do you have to be to hear an echo?

Question 3.

Question 4. In your group, discuss what things are done in venues that are larger than 17 metres to attempt to reduce echoes. Make a list.

Sometimes reflected sound is unwanted. eg echoes. On other occasions we can make use of the reflective properties of sound waves.

Complete the worksheet on reflected sound.