In order to produce a sound something has to vibrate.
The vibrating object causes sound waves in the air which make the ear drum in our ear vibrate.
There are two things that can change how you hear a sound
- The pitch of the sound. This is how high or low it is.
- The volume of the sound. This is how loud the sound is.
The speed of the vibrations decides the pitch of the note: Faster vibrations produce a note with a higher pitch.
The size of the vibrations decides the volume of the sound: If the size increases then the sound will get louder.
| The diagram shows a vibrating string. The string can be made to vibrate with a higher note 3 ways:1. Make the string tighter 2. Make the string shorter 3. Make the string lighter (a heavy object vibrates slower) |
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If we tighten the strings of a guitar the pitch will increase and the note gets higher
If we pluck the strings harder (or hit a drum harder) the volume will increase and the note gets louder
The speed of sound
Sound travels much slower than light.
This is why we see the flash of a gun before we hear the sound
Sound travels faster in solids and liquids than it does in air.
Sound will NOT travel through a vacuum.
How sound is produced in different musical instruments
| Instrument
Trumpet: Organ: Clarinet: Guitar: Piano: Drum: |
Part which vibrates
Lips Air Reed Strings Strings Drum skin |
Echoes
An echo is heard when sound is reflected off a distant object.
Sonar make use of echoes to measure the distance (or shape) of an object (eg the sea floor).
It does this by measuring the length of time it takes to hear the echo.
Ultrasound
Ultra sound is too high for us to hear.
It can be used to produce pictures of unborn babies,
| Sound facts: Frequency:=number of vibrations per second. Higher frequency = higher pitch Amplitude = size of the vibrations. Bigger amplitude = louderHumans can hear up to about 20,000 vibrations per second. Dogs can hear much higher notes |
How Sound travels
Sound travels in waves
Sound travels faster and better in solids and liquids than it does in air.
Sound will NOT travel through a vacuum.
We will not hear the sound of the moon exploding because there is no air in space between the earth and the Moon
| Sound travels much slower than light which is why we see a lightening flash before hearing it.
Sound travels at about 340 metres a second but light travels at 300 000 km a second (186000 miles a second) |
A string telephone
