Sound waves are produced when objects vibrate, creating vibrations that pass through air as disturbances. These disturbances are carried by the vibration of air particles passing the energy along from one to the next. Sound waves are mechanical waves that require a medium, like air, to travel through. They cannot travel through a vacuum. When sound waves hit a boundary like a wall, they can reflect back as an echo. Most music is now produced electronically by transforming electrical signals into vibrations in loudspeakers. Musical instruments produce sound by making their parts vibrate through being blown, plucked, hit or strummed.

1. 8.1- Making Sounds
Sir. Muhammad Abdul Mageid
Cambridge VIII
Physics – CHAPTER 8

2. Nature of Sound Waves

3. How sound waves are produced ?
 When objects vibrate they produce sound
 The vibrations create disturbances which pass through air
as Sound Waves
 The waves are carried out by particles (molecules of
gases in air) passing the vibrations along from one
particle to another nearby particle
 Each particle in air vibrate back and forth as the sound
wave passes

4. Nature of Sound Waves
 Sound Waves are Mechanical Waves
As they need a medium to pass(travel) through and
they can not travel through vacuum ( empty space)
 Sound Waves can not travel through vacuum because
there is no particles to pass the energy through

5. Echo
When sound waves reaches a boundary like a
wall it can reflect
Direction of echo
Direction of sound

6.  Is a sound that is repeated because the
sound waves are reflected back
 Sound waves can bounce off smooth
and hard objects in the same way as a
rubber ball bounces off the ground
Echo

7.  Most of music that we hear is now
produced by loudspeakers in Radios or
Headphones
 Transform electrical signals into sound
waves
Loudspeakers

8. Musical instruments
 Musical instruments create sounds by
making their parts vibrate
Example : Guitars make sound when their
string vibrate
 Different Parts of instruments vibrate when
they are hit , blown ,plucked or strummed

9. Musical instruments
Q- Place each of the following musical instruments into one of
three groups –hit ,plucked and blown- depending on the way in
which they produce sound
1- Trumpet
blown

10. Musical instruments
Q- Place each of the following musical instruments into one of
three groups –hit ,plucked and blown- depending on the way in
which they produce sound
2- Piano
plucked

11. Musical instruments
Q- Place each of the following musical instruments into one of
three groups –hit ,plucked and blown- depending on the way in
which they produce sound
3- Recorder
blown

12. Musical instruments
Q- Place each of the following musical instruments into one of
three groups –hit ,plucked and blown- depending on the way in
which they produce sound
4- Guitar
plucked

13. Musical instruments
Q- Place each of the following musical instruments into one of
three groups –hit ,plucked and blown- depending on the way in
which they produce sound
5- Cello
plucked

14. Musical instruments
Q- Place each of the following musical instruments into one of
three groups –hit ,plucked and blown- depending on the way in
which they produce sound
5- Drum
hit

15. Musical instruments
Q- Place each of the following musical instruments into one of
three groups –hit ,plucked and blown- depending on the way in
which they produce sound
6- Saxophone
blown

16. Musical instruments
Q- Place each of the following musical instruments into one of
three groups –hit ,plucked and blown- depending on the way in
which they produce sound
7- Mandolin
plucked

17. Musical instruments
Q- Place each of the following musical instruments into one of
three groups –hit ,plucked and blown- depending on the way in
which they produce sound
7- Harmonica
blown