Sound is the energy things produce when they vibrate (move back and forth quickly). If you bang a drum, you make the tight skin vibrate at very high speed (it's so fast that you can't usually see it), forcing the air all around it to vibrate as well. As the air moves, it carries energy out from the drum in all directions. Eventually, even the air inside your ears starts vibrating—and that's when you begin to perceive the vibrating drum as a sound. In short, there are two different aspects to sound: there's a physical process that produces sound energy to start with and sends it shooting through the air, and there's a separate psychological process that happens inside our ears and brains, which convert the incoming sound energy into sensations we interpret as noises, speech, and music. Sound is like light in some ways: it travels out from a definite source (such as an instrument or a noisy machine), just as light travels out from the Sun or a light bulb. But there are some very important differences between light and sound as well. We know light can travel through a vacuum because sunlight has to race through the vacuum of space to reach us on Earth. Sound, however, cannot travel through a vacuum: it always has to have something to travel through (known as a medium), such as air,water, glass, or metal. The first person to discover that sound needs a medium was a brilliant English scientist known as Robert Boyle (1627–1691). He carried out a classic experiment that you've probably done yourself in school: he set an alarm clock ringing, placed it inside a large glass jar, and while the clock was still ringing, sucked all the air out with a pump. As the air gradually disappeared, the sound died out because there was nothing left in the jar for it to travel through. When you hear an alarm clock ringing, you're listening to energy making a journey. It sets off from somewhere inside the clock, travels through the air, and arrives some time later in your ears. It's a little bit like waves traveling over the sea: they start out from a place where the wind is blowing on the water (the original source of the energy, like the bell or buzzer inside your alarm clock), travel over the ocean surface (that's the medium that allows the waves to travel), and eventually wash up on the beach (similar to sounds entering your ears). As a sound wave moves forward, it makes the air bunch together in some places and spread out in others. This creates an alternating pattern of squashed-together areas (known as compressions) and stretched-out areas (known as a rarefactions). In other words, sound pushes and pulls the air back and forth where water shakes it up and down. Water waves shake energy over the surface of the sea, while sound waves thump energy through the body of the air. Sound waves are compression waves. They're also called longitudinal waves because the air vibrates along the same direction as the wave travels.
I hope you read this...lots of good stuff in here....
13 Comments
Meirah
4/12/2016 04:15:05 pm
First commenter again
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Meirah
4/12/2016 04:15:41 pm
What luck!!!!!
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Caleb
4/12/2016 04:17:23 pm
i like cheez
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Pina colada man
4/12/2016 04:19:15 pm
new sale double the price pinacoladas
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Becca
4/12/2016 05:49:28 pm
That's so cool
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Lizzie
4/12/2016 07:03:45 pm
The slinky lab that we did in Period 1 was super awesome! It was really cool to see the sound waves.
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Dylan T
4/12/2016 08:15:45 pm
i like the first pic
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Olivia Sharp
4/12/2016 08:19:17 pm
Ya, me too!
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sammi
4/12/2016 08:40:04 pm
hay do u guyz want to hear a joke (or read one)
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Hailey
4/12/2016 09:52:45 pm
I love learning about this!!!!
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Emma
4/12/2016 11:27:01 pm
That's sooo cool!!
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Mrs. TaylorI love science! Everything about the world is interesting and never boring. I love to study plants, animals, insects, and people. My favorite subjects are my students who are the most unique organisms on the planet! Categories |