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.
Silence
There is a flat line when there is no sound. The air molecule aren't vibrating.
Quiet Sound
The trace goes up and down. It has a small amplitude.
Loud Sound
The trace goes up and down much more. The amplitude is much greater.
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.
High-Pitched sound
The waves are very close together. The molecules are vibrating more times every second.
Low-Pitched sound
The waves a far apart. The sound has a lower 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