This document discusses the fundamentals of sound. It explains how sound travels through air and water from a source to the ear. It also discusses how telephones and mobile phones convert sound to electrical signals that can be transmitted through wires or radio signals and then back to sound. The document covers different sources of sounds like bells and their pitches. It concludes with a summary of the key points learned, such as how vibrating objects produce sound, and how large and small objects affect the frequency and loudness of sounds.
4. 4
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.
5. 5
Telephones --
The message travels through miles
of wires as an electrical signal.
microphone
loudspeaker
electrical signal
6. 6
Radio signal
Mobile phones use radio
Sound - electrical signal - radio signal - electrical signal - sound
In one phone the
sound is changed
into an electrical
signal then into a
radio signal.
Sound - electrical signal - radio signal - electrical signal - sound
In the second phone
the radio signal is
changed into an
electrical signal then
into sound.Mobile
phone
beacons
13. 13
What have we learned?
Vibrating objects make sounds
Sound needs a medium through which to travel
– 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.
15. 15
Ultrasound is very, very high
frequency sound.
It is used to see inside people
- to see
babies before
they are born
if a heart is
working well
blood flow