Sound

How is is made, changed or heard?

What is Sound?

Sound is vibrations travelling through the air or other materials. it can be made by anything. It's very easy to make sound. You can clap your hands or break a twig. You can make sound with your vocal cords too. If you put your hands on your throat, you will be able to feel the vibrations.

How is Sound Made?

Vibrations

When an object vibrates, it creates sound. The amplitude of the vibration is the maximum distance the vibrating object moves from its rest position before starting to vibrate. The frequency is the number of vibrations per second. It is measured in Hertz (Hz).

Loudspeakers

Loudspeakers are used to produce sound emitted from computers, radios and other electronic devices. Inside a loudspeaker, a cone vibrates back and forth to create the sounds that we hear.


If we turn the volume up, the cone will vibrate more to create a louder sound. It will vibrate more frequently if the sound is higher.

How is Sound Changed

Changing Sounds

There are three types of musical instruments: string, wind and percussion instruments. Musicians can learn to change the loudness and the pitch of their instrument. They change the loudness to make the sound louder or softer and the pitch to make the sound higher or lower.

Changing Amplitude

The oscilloscope allows you to see the sound wave as a line on the screen. This is called a trace.

Changing Pitch

The pitch of a sound tells if it is high or low. On an oscilloscope, a high-pitched sound, the waves will be close together. On a low-pitched sound, the waves are spread out. To increase the pitch, the sound must have a higher frequency.

How is Sound Heard

How Sound Travels

The vibrations travel outwards from the source that created the sound. Sound can travel very easily through air, solids and liquids. Sound cannot be heard in a vacuum because there is no material to travel through. The vibrations are passed on from molecule to molecule. This is called a sound wave.

The Ear

Once a sound is emitted, the vibrations travel down the ear canal. Then, the vibrating air pushes on the eardrum and the eardrum pushed three small bones so that they vibrate too. The vibrations hit against the cochlea, which is filled with liquid. Then, the liquid simulates nerve cells and sends electrical impulses to the brain.

Hearing Range

Younger people have very good hearing. As you get older, you gradually lose the ability to hear. Most people can hear sounds as low as 20Hz. A young person can hear sounds up to 20,000Hz. Sounds above 20,000Hz are called Ultrasounds.


Unwanted sounds is called noise. Loud sound can damage you ear and it could make you deaf.

Sources

- Cambridge Checkpoint Science Coursebook

- Cambridge Checkpoint Science Workbook