Sound And How It Travels (1963)

[Music] la [Music] it's another fine day at the beach but for Sue and Steve it's not an ordinary day their vacation is coming to an end Steve wants to remember everything just as it is what he sees around him and especially the different sounds of summertime some high some [Music] low some loud some soft So Soft you have to listen carefully to hear them and here is a vacation sound you can take home with you sue has a seashell in which she says you can hear the RO Ro of the ocean there are so many sounds to [Music] [Music] remember Tommy's been learning to play the guitar he ought to know something about sound maybe he can explain it to [Music] them first Steve wants to ask him how sound is made just using his guitar Tommy can show how all sounds are made that's right every kind of sound high or low loud or soft is made in the same way watch do you see how the string is moving we look at this closely we see a steady movement back and forth again and again that movement is called vibration and vibration is the cause of all sound the sounds of a guitar the sounds of birds or boats they are all made by [Music] vibration when something vibrates to make a sound it moves the air around it much as a stone moves water when you drop it in a pool this is how the vibrations of sound travel through the air to our ears it takes time for these vibrations to travel sometimes we can see how much time it takes for sound to move through the air we can see a ship blowing its whistle out there in the bay but we can't hear it until the wave of sound vibration has traveled to our ears Sue notices that even after she has turned her head away she can still hear the [Music] whistle when a boat goes out of sight will she still be able to hear it as if nothing were in the way Sue hears it because sound waves just like these ripples of water change direction or bounce back when they strike against something if sound travels through air will it also travel through water let's try a little experiment to find find out Steve's a good swimmer so he will go underwater to listen while Sue will hold her Stones underwater and hit one against the other like this hey it Works Steve got a little wet but he and Sue discovered something sound does travel through water Tommy has another idea there are more ways to find out about sound let's use this fence to discover if sound will travel through wood as well as water for this experiment Sue moves all the way down here Ready set go hey that was loud Sue discovers that sound not only travels through wood but is louder than sound traveling through air we can use the fence to demonstrate something else about sound listen to the noise the stick is making now listen to what happens when Steve holds the stick this [Applause] way notice how much higher it sounds when the stick is held shorter Steve sees an interesting gate will the short pickets sound higher than the long ones [Applause] Tommy says he can do the same thing with his guitar when he picks this string it sounds like this how do you suppose the same string will sound when he holds it down here when Tommy shortens the string by holding it down it vibrates faster and when vibration is faster the sound it makes is higher the same way Steve stick made a different sound when he held it in a different way when Tommy lets the whole string vibrate the sound is lower because the vibration is slower but as he shortens the string the vibrations become shorter and faster and the sound becomes higher [Music] Tommy knows a lot about the guitar but what is he up to now with this drum Tommy asks them to watch carefully maybe they'll see something unusual he says he can make the sand dance to his [Music] music can you see it when this tone is played near the drum the drum begins to vibrate too Steve and Sue were surprised to learn that this is the way we hear sounds inside each of our ears a stretched piece of skin called an eardrum vibrates to all the sounds we hear and see how the outer ear is shaped like a funnel to help gather sounds from the world around us the sounds of Music the sounds of nature sounds that warn us sounds that teach and tell that slow ahead St hard for all of these sounds are made by vibration vibration that travels out in all directions sound takes time to travel from one place to another but it can be heard even when we can't see what is making the sound Steve and Sue found out that sound moves through water as well as through wood and we learned that length has a lot to do with whether a sound is high or low the day is almost ended now it's time to go Sue is going to take her shell home with her the sound she hears isn't the ocean after all but it will help her to remember this vacation at the beach and what she and Steve learned about The Sounds around us [Music]