12 Bush telephone game Sound travels through the string
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. microphone loudspeaker electrical signal
15 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
24 What else changes sounds? How do you tune a violin? Let us try to make a string instrument.
25 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.
26 Can you spot the baby? Sound has lots of uses
27 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
28 Knowledge about sound helps - Musical instrument design 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 Physics is everywhere From kittens ears to mobile phones