Sound. W h a t i s S O U N D ?. Sound is longitudinal pressure waves that travel through elastic media. We can produce these vibrations by : Making a column of air vibrate, plucking a string, or by hitting an object. Sound Waves.
Sound is longitudinal pressure waves that travel through elastic media.
Sound Waves are caused by a source vibrating to and fro and causing successive compressions (squashing) and rarefactions (spreading out) in the medium; hence sound cannot travel in a vacuum.
Sound waves are received by the ear, and interpreted by the brain.
Sound can vary in pitch– howhighorlowa note is.
It can also vary involume –howloudor howsoftthe note is
An amplifier makes the sound louder. We talk about the amplitude of the wave, which tells us how much energy there is. The taller the wave the louder the sound because more energy has been put in
The loudness depends on how much energy the sound wave has.
In an electric key board an amplifier makes the sound louder.
A louder note has a bigger amplitude. (height)
Loudness is measured in decibels dB
These help to make sound louder so the amplitude or height of the wave would be higher. The wave has more energy
The pitch depends on how many vibrations there are.
The more frequent the vibrations the higher the note.
The fewer the vibrations the lower the note
The higher the note, the more waves per second so the waves are squashed together.
The waves will have a short wave length.
The lower the note, the FEWER waves per second so the waves are spread out.
The waves will have a longer wave length.
Different instruments produce different shaped wave traces.
The extra wiggles are known as harmonics. These give the instrument its “colour”.
Most instruments usually produce many frequencies or harmonics at the same time. All the harmonics add together to make a complicated waveform.
Here are some synthesized wave traces each shape represents a different kind of sound.
On the next few slides you will find internet sites that you can visit by clicking on the web address
How Stuff Works article on CDs and CD playerswww.howstuffworks.com/cd.htm
How tape recorders workwww.howstuffworks.com/cassette.htm
Short BrainPop movie about CDs and DVDswww.brainpop.com/tech/musicandsound/cd/index.weml
How CDs work, with an animated diagrammicro.magnet.fsu.edu/electromag/java/cd/
How CDs and CD players workwww.discoverengineering.org/eweek/cool_things/cd/index.htm
How analogue and digital recording workswww.howstuffworks.com/analog-digital.htm
The technology of vinyl records compared with CDswww.pbs.org/ktca/newtons/11/cdlp.html
An animated look at how a speaker worksmicro.magnet.fsu.edu/electromag/java/speaker/
Watch a movie about soundwww.brainpop.com/science/sound/sound/index.weml
Take an underwater sound quizwww.pbs.org/wgbh/nova/subsecrets/sounds.html#02
Find out why sonic booms occur, with help from a speeding motorboatwww.howstuffworks.com/question73.htm
How bats use echolocationmembers.aol.com/obcbats/ecolocation.html