eLimu

Sound energy

Sound

  • Sound is made when things vibrate.
  • Vibration is a random movement of objects.
  • Sound travels in all directions.
  • We hear sound with our ears.

Sources of sound

  1. Animals
  2. Bell
  3. Radio
  4. Vehicles
  5. Drum
  6. Whistles
  7. Horn
  8. Telephone
  9. Ambulance
  10. Running water

Animal sounds

  • A cow moos.
  • A dog barks.
  • A cat meows.
  • A lion roars.
  • A cock crows.
  • A hen clucks.
  • A duck quacks.
  • A pig grunts.
  • A rat squeaks.
  • A bee/mosquito buzzes.
  • A sheep bleats.
  • A buffalo bellows.
  • An elephant trumpets.

Sound from other things

  • A bell/telephone rings.
  • We beat/hit a drum to get sound.
  • We blow a horn/whistle to get sound.
  • We pluck a guitar to get sound.

Special sounds

  • These are sounds with special meaning.
  • The sound of an ambulance means someone is being rushed to the hospital.
  • A police siren warns of danger.
  • A bell tells us it’s time to do something else.
  • A telephone rings when someone is calling.

- Sound is a form of energy that is caused by vibrations.

- When you hit a drum, it's caused to vibrate thereby releasing the sound that you hear. 

 

Sources of sound

Anything that produces its own sound is referred to as a Source of sound.

Examples of sources of sound in our surroundings are animals, drums, bells, and whistles.

Ways of producing sound

Sound can be produced in many ways.

Two common ways of producing sound are by plucking objects and hitting objects.

When we pluck or hit an object, we cause it to vibrate meaning the object moves to and from repeatedly creating sound.

An object that can be plucked is a tight string, for example, a guitar string.

An object that can be hit is a drum or a tin.

Direction of sound

Sound moves in all directions.

For example, if you pluck a guitar string its sound will be heard by anyone standing in any direction from where the guitar is played.

Similarly, a drum hit at the center of a hall can be heard in every corner of the hall.

However if one listens carefully he/she can identify the direction from which the sound comes from.

Cats and dogs move their ear lobes to find out the direction the sound is coming from.

 

Special sounds

When we talk or sing we produce sounds with our mouths.

Whatever one says while talking or singing has meaning.

Similarly, objects around us make sounds that have particular meanings.

These sounds are made at particular times to inform someone about something specific.

Examples of special sounds include:

  • Hooting: Move out of the way.
  • Ambulance siren: Move out of the road and let the ambulance pass. There is an emergency.
  • Screaming: Something dangerous or exciting is happening
  • Ringing bell: You are being alerted or reminded that something you are aware of is happening.

At school, it means it is time to change from one lesson to another.
In offices, it may mean fire.

  • Fire engine siren: There is need to move out of the way and let the fire engine proceed to where fire or danger might be. It also means an emergency.

 

Types of sound

Sound in our surroundings can be classified into LOUD or SOFT sounds. 

Loud sound

If you increase your voice or the volume of a radio, that sound is referred to as loud sound.

Soft sound

The sound you produce when you whisper is referred to as soft sound.

Similarly, when you reduce the volume of your radio it will produce soft sound.

Pollution from sound

Pollution means to contaminate, anything useful to us.

Sound can pollute the air if it is too loud.

In other words, very loud sounds like loud music or shouting and screaming is not good for the environment.

Loud sound affects living things.

It can cause irritation and harm to our eardrums.

Livestock like poultry are also affected by a loud sound.

Loud sound gives them stress and they may not be able to reproduce or lay eggs.

Therefore to avoid pollution from sound, all sound should be soft.

 

KCPE Topical Questions

10.5 STANDARD 5 

10.5.1 Sound 

1. Which one of the following methods will NOT increase the pitch of a note made on a stringed instrument?

A. Plucking the string harder     B. Tightening the string
C. Making the string shorter      D. Making the string thinner

 

2. Through which one of the following is the transmission of sound poorest?

A. Metal      B. Water      C. Wood         D. Air

 

3. Which one of the following DOES NOT allow sound to pass through?

A. Air       B. Water      C.  Vacuum      D. Wood