Here we focus on those scientific concepts that are the hardest to explain to children. We break it down into what pupils need to know and outline the background science. Even though much of the background science does not need to be taught to primary aged children, it is useful for you as a teacher when addressing misconceptions and children’s challenging questions.

Please refer to your national curriculum documents when planning your sequence of work and ensure that you teach the correct knowledge for your year group.

What do children need to know about sound?

Sounds are ever-present and all around us and therefore learning about sound might appear straightforward. However, this familiarity is often what leads to misconceptions. Learning about sound is best approached in an exploratory and hands-on way, giving children the opportunity to really experience what happens when sounds are made. We have included some ideas for how to teach sound in part two of this topic guide.

Key scientific concepts: Pupils need to...

1. Know that sounds are caused by vibrations.
2. Recognise that sounds need a medium (substance) to travel.
3. Know that pitch describes how high or low a sound is.
4. Know that volume describes how loud or quiet a sound is.
5. Know that sounds get fainter with increased distance from the sound source.

1. Sounds are caused by vibrations.

Pupils need to know:

• Sounds are caused by something vibrating.
• Sources of sound include musical instruments, loudspeakers and the human voice.
• A variety of things can vibrate to create a sound, such as: the air in a flute, the string on a guitar; the vocal cords in the throat or skin on a drum.

Background science for teachers

Sounds are made when objects vibrate. The vibrating source acts on the medium that surrounds it, for example air, making the particles in the medium start moving back-and-forth in a way that matches the movement of the source. These vibrations travel through the medium in all directions until they reach a detector like our ear drum.

When you hear the sound of a violin, the source that created it is the vibrating strings. For the purr of a cat, the source that created it is its vibrating vocal cords.

Our ear drum is made to move by the vibrations in the medium (usually air) that it is in contact with. The movement in the ear drum matches the back-and-forth movement of the medium.

This animation shows how air particles vibrate to transmit sound from a loud speaker to an ear.

2. Sounds need a medium to travel.

Pupils need to know:

• We call the material that sound travels through a medium.
• Sounds can travel through solids, liquids, and gases.
• Some materials are good at absorbing vibrations from sounds and making them quieter. We can use these to protect our ears from loud sounds.  
• The structure and function of sensory organs, including the human ear. (Scotland only)

Background science

Sounds are made when something vibrates and these vibrations travel through the air, or another medium, as sound waves. Pupils may think that sounds can only travel through air but they also travel through solids and liquids. A variety of hands-on practical activities where pupils experience hearing sounds through gases, solids and liquids will prevent this misconception forming (This Teach Engineering video is a good starting point)

Sounds can travel through any medium if there are enough particles in a specific volume of the material to allow the back-and-forth movement of one block of particles to be passed on to the neighbouring block of particles. Particles are arranged differently in solids, liquids and gases and the forces between particles are different in each medium and this affects how quickly sound vibrations can pass through them. Sounds travel faster and further in solids; they can also travel quite fast and far in liquids which is how whales communicate with each other. Sound travels slowest in gases. For example 340 metres per second in air, 1500 metres per second in water and 6000 metres per second in a solid.

When sound travels through the air into our ears, pupils may think that the air particles move from the sound source to the ear. But this is not the case. It is the vibration that is passed from one air particle to the next, until it reaches the ear drum.

Below is a step-by-step guide on how the structure of the ear allows us to hear.

• The vibrations enter the air in the outer ear and travel through a narrow passageway called the ear canal, which leads to the eardrum.
• The eardrum vibrates matching the back-and-forth movement of the air and sends these vibrations to three tiny bones in the middle ear.
• These bones amplify the sound vibrations and send them to the cochlea, a snail-shaped structure filled with fluid, in the inner-ear.
• This fluid is made to vibrate. Hair cells (sensory cells) in the cochlea detect the sounds and stimulate an electrical signal. The auditory nerve carries this electrical signal to the brain, which turns it into a sound that we recognise.

Our hearing is easily damaged by regular and prolonged exposure to loud sounds and any sounds above 85 decibels can cause permanent and long-lasting damage to our hearing. You can protect your hearing at a concert or at work by wearing ear plugs or ear defenders made from soundproof materials which are often spongy, such as acoustic foam, memory foam or silicone.  

Image credit: Ear-anatomy-text-small-en.svg via Wikimedia

Diagram of the inner ear.

3. Pitch describes how high or low a sound is.

Pupils need to know:

• Sounds can vary in pitch, which can be high or low.
• Pitch is linked to features of the sound source for example the length, thickness and tightness of strings, or the size of a drum and the tightness of its skin.

Background science

The pitch of a sound that you hear is determined by the frequency (how many times something vibrates in one second). The higher the frequency, the higher the pitch of the sound you hear. Frequency is measured in hertz (Hz) where 1Hz means one vibration per second. The pitch of a sound depends on the frequency of vibration of the source which depends upon its features, such as the length, thickness and tightness of strings or the length of an air column.  For example, as the length of a vibrating object increases, the frequency of the sound it produces decreases creating a lower pitched sound.

The frequency of a sound does not affect the speed of a sound wave. Speed of a wave depends only on the material through which the wave is travelling.  (See section 2)

4. Volume describes how loud or quiet a sound is.

Pupils need to know:

• Sounds can vary in loudness.
• Loudness is linked to the size of the vibrations causing the sound.

Background science

The loudness of a sound is determined by the size of the vibrations. Bigger vibrations make louder sounds, smaller ones make quieter sounds. If a loudspeaker cone moves back-and-forth over a larger distance, it causes a bigger disturbance in the air and results in a louder sound.

Loudness is subjective, it depends on the listener and how well their ears are functioning. To measure and compare the loudness of sounds we measure the amplitude of the vibration. Our ears respond to sounds in a way that large increases in the amplitude of the vibrations are registered as small increases in loudness. Sounds are usually measured in decibels which matches the way in which the ear registers sounds, going from 0dB that marks the threshold of human hearing to 140bB at the threshold of pain.

Comparing how animals including humans, hear sounds is an important connection to make in relation to children’s understanding of the differences between species. Humans, for example, have inferior hearing ability compared to many other animals because our ears are not as large and cannot move independently, which is why we rely more heavily on our sight. Identifying these differences is necessary for understanding how animals can survive in their environment.  This BBC video explains how different animals communicate and this one explains how they hear.

5. Sounds get fainter with increased distance from the source.

Pupils need to know:

• Sound vibrations travel in straight lines spreading out in all directions from the source.
• The loudness of a sound depends on the size of the source’s vibration and the distance you are from it.  

Background science

Sound vibrations travel in straight lines spreading out in all directions from the source through a material such as the air.

The loudness (volume) of the sound reaching a detector or your ear depends on three things:

• The size of the source’s vibration.
• The distance of the detector from the source (because the sound vibrations spread out in all directions)
• The medium the sound travels through (eg. a gas like air or a solid or liquid).

Pupils may think that the changes they observe and measure in the volume of sound with distance from the source is to do with the speed that sound is travelling. This is not the case, as the speed that the sound vibration travels at depends only on the material it travels through. 

Useful related resources      

The Ogden Trust: Phizzi focus: Sound

This resource highlights the opportunities for pupils to explore and investigate sound and encourage children to make cross-curricular connections.

Ideas to try with your class 

Now you've got the tricky scientific concepts under your belt, try our ideas to help you explore sound with your class in a way they will understand in part two of this topic guide! 

You can also take a look at the related topic guides for animals including humans, light and materials.

Many thanks to the Ogden Trust, who have collaborated with Explorify to produce this 'Tackle the tricky bits' page.

Image credit: Sounds of Nature by Sergey Nivens via Canva