Changing Sounds

Changing Sounds

Sound is a form of energy. For sound to be produced vibrations must be set up by a source.  This is done by hitting (drum), blowing (recorder), stroking (sand paper on wood) and electrical (loudspeaker).

The vibrations travel through a solid liquid or gas and reach our ears where it can be heard.  If the vibrations have a lot of energy then they are loud.  If they have little energy then the sound is quiet.  Sometimes the vibrations can be seen or felt on the skin.

In air, sound travels at 1,160 km per hour, but speeds up in water to 5, 400km per hour.  Things which travel faster than sound are called supersonic.  The Concorde can travel faster than sound.

Dolphins communicate with each other under the sea.  The sound can travel for hundreds of miles, much further than in air.  Sound travels even more quickly through a solid metal than through the air or water.  Standing near a railway line, a humming from the rails can be heard several minutes before a train itself can be heard directly.  

Sound travels through solids and liquids as well as air.  Sound cannot travel through a vacuum.  Sound travels at different speeds in different substances.  This is because different substances are made up of particles in different ways.  The sound pushes the particles and as it travels it moves from one particle to another.  In a gas the particles are far apart, so some of the sound energy is lost when trying to push one particle into another one. Therefore the speed of sound is slow so it will not travel as fast as it does in substances where the particles are closer together.

Pitch is the highness or lowness of a sound.  A high pitch is caused by short vibrations and a low pitch is caused by long vibrations.

The pitch of a note produced by a guitar depends on the length, thickness and tension of the string.  A shorter, thinner, tighter string produces a high pitch and a longer, thicker, looser string produces a low pitch. On a guitar the strings can be shortened by putting a finger on the fret board.

In a wind instrument a column of air is set vibrating and the pitch depends on the length of the column.  A long column makes a low pitch and a short column makes a high pitch.

The loudness (volume) of the sound depends on the amount of energy the vibrations contain and the rate at which this energy is transmitted.  If a string is plucked hard the vibrations will contain more energy and the sound will be louder than if it were plucked more gently.   

Questions

1. What is sound?
2. Sound is the brain’s interpretation of waves of pressure travelling through a medium. Waves of pressure can be produced
3. by any vibrating object like the strings of a guitar, drums or our own vocal cords.
5. How is sound produced? Sound is produced by vibration of an object.
7. What do sound vibrations travel through? Sound travels through solids and liquids as well as air. Sound can not travel thorough a vacuum.
9. Through which substance does sound travel fastest? The
11.               Why is this? because it can travel faster than sound.
14. Why do you think sound cannot travel through a vacuum? Because there is no molecules in a vacuum and if something doest;t have molecules in it sound won’t be able to travel through it.  
16. What is pitch?
17. How would you create a high pitch on:
1. A guitar?
2. A recorder?
3. A drum?
18. What does the volume of sound depend on? If it’s low or high.
20. How would you play a drum quietly? By hitting the drum softly with the stick.  
22. How much energy do you think the vibrations would have if you did this? A low amount of energy.

23. If the vibrations had lots of energy, what would the volume be like? Powerful and will be very loud and probably travel faster.

Use the words below in the reading passage.

hitting     vibrations     plucking    blowing     energy     liquid   sound     felt    loud     quiet    air   sea    high    long     water

blow   low     short       finger

Changing Sounds

Sound is a type of _____ energy ____.   Sound is produced by ____ __ sound _____.

Vibrations are made must by _____hitting____ a  drum, _____blowing_______ a recorder,  ______plucking_____ a string.

_____sound  ______ can travel through a solid _____ liquid____ or gas and reach our ears where it can be heard.  If the vibrations have a lot of energy then they are ___loud____.  If they have little energy then the sound is ___low_____.  Sometimes vibrations can be ____felt___ on the skin.

Sound travels faster in a solid than in ____sea_____.  It travels faster in water than it does in _____air_______.

Dolphins communicate with each other under the ___water___.  

Pitch is the highness or lowness of a sound.  A ____ quiet___ pitch is caused by short vibrations and a low pitch is caused by ____ high____ vibrations.

The pitch of a note produced by a guitar depends on the length, thickness and tension of the string.  A shorter, thinner, tighter string produces a high pitch and a longer, thicker, looser string produces a low pitch. On a guitar the strings can be shortened by putting a  ___ finger

______ on the fret board.

When you __blow______ into a wind instrument the air vibrates.  The pitch depends on the length of the column.  A long column makes a __short_____ pitch and a ____ long____ column makes a high pitch.

The loudness (volume) of the sound depends on how hard a string is plucked.  The sound will be louder the harder it is plucked.