13. 13
Telephones --
Are like a sound system
The electrical
signal is
amplified
A microphone
changes sound to an
electrical signal.
A loudspeaker
changes the electrical
signal to sound.
14. Telephones --
The message travels through miles
of wires as an electrical signal.
14
microphone
loudspeaker
electrical signal
15. Mobile phones use radio
Sound - electrical signal - radio signal - electrical signal - sound
In one phone the
In the second phone
sound is changed
the radio signal is
into an electrical
changed into an
signal then into a
electrical signal then
radio signal.
Mobile into sound.
phone
beacons
15
Radio signal
Sound - electrical signal - radio signal - electrical signal - sound
24. What else changes sounds?
How do you
tune a violin?
Let us try to
make a string
instrument.
24
25. What have we learned?
Vibrating objects make sounds
Sound needs a medium through which to travel
25
– air, water, string - - -
The medium vibrates but does not travel with the
sound
Large vibrations make loud sounds
- small vibrations make quiet sounds
Large objects make low frequency sounds
- small objects make high frequency sounds
In strings the frequency of the sound depends
on the length, thickness, and tension.
26. Can you spot the baby?
26
Sound
has
lots
of
uses
27. Ultrasound is very, very high
frequency sound.
It is used to see inside people
- to see
babies before
27
they are born
if a heart is
working well
blood flow
28. Knowledge about sound helps -
Musical instrument design
28
and playing them
Sailors find how deep the water is
Building design
so we hear sounds clearly in meetings
so sound does not travel through walls
Sound systems for everyone
radio - CD players
mobile phones - iPods
29. 29
Physics is
everywhere
From kitten’s ears to mobile phones