Introduction
Sounds are vibrations that can travel through different materials. The pitch of a sound is how high or low the sound is. The loudness of a sound is how loud or soft it is.
Sounds are vibrations
Sounds are made when objects vibrate. The vibration makes the air around vibrate, and the air vibrations enter your ear. You hear them as sounds.
You cannot always see the vibrations, but if something is making a sound, some part of it is always vibrating.
Sound vibrations can travel through different materials
Sounds as vibrations can travel through many different materials.
- Sound can travel through solids, like metal, stone and wood.
- Sound can travel through liquids, like water.
- Sound can travel through gases, like air.
Sound vibrations travel better through some materials than others. For example, sound vibrations travel very well along metal pipes.
Sound cannot travel through a completely empty space (a vacuum), which has nothing, not even air, in it. If there is a vacuum between a sound-making object and our ears, we won't be able to hear the sound.
Pitch of a sound
A short string gives a higher-pitched sound than a long string when they are plucked.The pitch of a sound is how high or low the sound is. A high sound has a high pitch and a low sound has a low pitch.
- A tight drum skin gives a higher-pitched sound than a loose drum skin.
Loudness of a sound
A guitar string plucked strongly makes a loud sound. A guitar string plucked gently makes a soft sound.The loudness of a sound is how loud or soft the sound is.
A drum skin hit hard makes a loud sound. A drum skin hit gently makes a soft sound.
Loud sound
A recorder blown hard makes a loud sound.
Soft sound
A recorder blown gently makes a soft sound.
http://www.bbc.co.uk/bitesize/ks2/science/physical_processes/changing_sounds/read/5/
