Because sounds are made when objects vibrate, there must be a material for there to be sound.
Sound cannot travel through a vaccuum because there is nothing to pass along the vibrations.
In space, no one can hear you scream - because there is no air to pass along the sound vibrations.
If two astronauts want to talk to each other in space, they have to use a radio, or get their helmets touching together and shout.
A dense material like wood allows sound waves to pass very well; this is why a lot of musical instruments are made of wood, or have wooden sound-boxes. Try banging a metal fork on a wooden table and listening to the sound pass through the wood.
You should be able to hear a tone from the vibrating fork, passing through the table to your ear.
Sound also travels through water. Wales use this fact when they sing to each other. Sound actually travels more than 4 times faster through water than through air.
can make a string telephone to see how sound travels through solid
materials. All you need are two plastic cups and a length of string.
Drill a small hole in the bottom of each plastic cup, and thread through the string. Fix the string in place by tying a knot or using glue.
Give one cup to a friend and stretch the string tight between you. If the string is floppy, the sound will not pass. If you pull too tight, the string will pull out from the cup, and you will have to start again!
Get your partner to talk to you through their cup, wile you listen at your cup. The sounds should travel along the string from cup to cup, as long as the string is tight.
Does sound travel through jelly? We did an experiment to see if soundwaves will travel through strawberry jelly.
We used a signal generator to make a sound, and connected this to a small waterproof speaker. We put this speaker into a lump of jelly.At the other end of the jelly we placed a waterproof microphone, and connected this to the microphone port of a PC. The PC was running some oscilloscope software to show whatever the microphone recieved.
Now we know sound travels through all sorts of materials. Some better than others.
The poor conductors of sound are Sound Insulators. We could use these materials to block or muffle sounds.
designed by Andy Lakin-Hall.
C.E. Primary School. Edenbridge, Kent. TN8 6RP.
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