New
New
Year 7

Reflecting and absorbing sound

I can describe factors that affect how much sound a material or object might reflect or absorb, and explain ways to reduce noise.

New
New
Year 7

Reflecting and absorbing sound

I can describe factors that affect how much sound a material or object might reflect or absorb, and explain ways to reduce noise.

Lesson details

Key learning points

  1. Sound reflects from hard surfaces. An echo is when a sound is heard again after reflecting and travelling back.
  2. Smooth, flat surfaces help to produce echoes. Irregular surfaces reflect sound in many directions, spreading it out.
  3. The particles of harder materials are held together by stronger forces so sound waves can’t make them vibrate much.
  4. Soft surfaces absorb a lot of sound because sound waves transfer energy by making the particles in them vibrate.
  5. Noise (unwanted sound) can be reduced by using soft materials to absorb it or hard materials to reflect it.

Common misconception

Pupils often describe an absorbing surface as trapping a sound and do not correctly describe how the vibrations of air particles are reduced by making particles in a surface vibrate more.

Provide opportunity for pupils to describe how vibrations of air particles are reduced when sound waves make particles in a surface vibrate more.

Keywords

  • Reflect - to ‘bounce’ off a surface

  • Echo - when a sound is heard more than once because sound waves have reflected back

  • Transmit - to pass into and through a material

  • Absorb - materials that absorb sound reduce the vibrations of the air (as sound is easily transmitted to/through them)

  • Noise - unwanted sound

Echoes are heard best following a short loud sound, such as two blocks of wood being hit together or a short shout. There are excellent videos available online about sound proofing and 'anechoic chambers' (testing chambers designed to minimise echoes (reflections of sound) to almost zero.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Loading...

6 Questions

Q1.
Which of the following words describes a repeated back and forth movement?
vacuum
Correct answer: vibration
violin
voltage
volume
Q2.
Which of the following words is used to describe what all solids, liquids and gases are made of?
Correct answer: particles
partitions
parts
pinnacles
popsicles
Q3.
A drum on one side of a room is hit. It makes a sound that travels to the other side of the room. How does the sound travel across the room?
Air travels from one side of the room to the other.
Sound particles travel from one side of the room to the other.
Sound passes between the air particles from one side of the room to the other.
Correct answer: A pattern of repeating movements travels from one side of the room to the other.
Q4.
What is the name of the process when a wave ‘bounces’ off a surface?
absorption
diffraction
Correct answer: reflection
refraction
transmission
Q5.
What name is given to the process when a wave loses its energy after travelling into a material, so that it neither bounces off nor travels all the way through?
Correct answer: absorption
diffraction
reflection
refraction
transmission
Q6.
When a sound wave travels through air, it makes the air heat up a little. Which of the following statements explains why this happens?
The wave uses up air particles.
The wave creates more air particles.
Correct answer: The wave increases the random movements of air particles.
The wave decreases the random movements of air particles.

6 Questions

Q1.
Which of the following statements are correct?
Correct answer: When an object absorbs sound, its particles vibrate more.
Correct answer: Softer materials absorb more energy from sound waves than harder materials.
When a sound wave enters a solid, it travels through gaps between particles.
Q2.
A person hits a drum in a room. After they stop hitting the drum, they cannot hear the sound any more. Which of the following statements explains why this happens?
The energy of the sound has been used up.
Correct answer: The sound wave has been absorbed by walls and other objects.
The sound can now be heard somewhere else instead.
Correct answer: The energy of the sound has transferred to the thermal store.
Q3.
A person stands 5 metres away from a wall outside and claps. They hear an echo. When the person hears the echo, how far has the sound wave travelled?
0 m
between 0 m and 5 m
5 m
Correct answer: 10 m
20 m
Q4.
Which of the following characteristics of a surface allow it to produce clear echoes?
Correct answer: flat
rough
Correct answer: smooth
Q5.
Which of the following is the correct definition of ‘noise’?
loud sound
constant sound
Correct answer: unwanted sound
sound that stops and starts
Q6.
In a music recording room, echoes are usually not wanted. Which of the following methods are most effective at reducing echoes in the room?
wooden floor
Correct answer: carpet on the floor
Correct answer: walls covered with soft foam
walls covered with metal sheets