1. Nature of Sound Waves

This last video in our first week will bring together some more about sound travel and transmission.

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So a couple of things we wanted to think about maybe more firmly define something like the term waves.

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So waves is referring to the disturbance being composed of vibrations that move within a medium, The vibrations that move within a medium.

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OK And to maybe more firmly talk about medium, it refers to interconnected particles.

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So something like air is a medium that has is formed of lots of different particles and can transport or transmit that sound energy.

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So let's get back to our idea of a wave in sound.

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We've all heard of like, oh, the sound waves finally got to me.

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What do we mean by waves?

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So waves is that disturbance that's really made of vibrations that travel through a medium.

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So there's several squares on your handout.

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So here is our maximal displacement, and there's the highest pressure.

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So all of these dots are molecules, and there's a lot of them in a small amount of space that is called a condensation.

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And then when they're more spread out, when there's maximal movement in the opposite direction.

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That would be the rare faction.

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So if we look at like the density of molecules at various points in the sound transmission, we have really across sound travel, the space between between particles changes.

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And there might be times that we want to talk about, you know this wave of motion and that can get really, really hard to talk about if you had to draw all these little dots.

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So a way to talk about it is to more look at this visual plot of a wave.

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So we have those points of compression where there is a positive pressure and there's a great deal of pressure in those areas of condensation.

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And then once more a rare faction would be would equal a negative pressure.

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There's a lot more space for a few molecules to travel.

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So that's an area of negative pressure.

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So the cycle continues on for the duration of a sound.

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So let me show a couple of illustrations.

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They're actually just one right in.

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Here is another illustration.

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So the light color is representing the rarefaction and the dark color here would illustrate A compression.

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So here's an animated form of the sound waves.

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So each of that those areas of high pressure, each of those compressions will continue to travel.

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So a molecule is going to bump into one to a neighbor and that will displace the next molecule.

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So our area of disturbance continues to travel.

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So we have taken a microscopic view of like 1 molecule being displaced.

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If we let me maybe change a color and use this example here, I'm going to switch colors real quick to a red.

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So if we followed 1 molecule, it might travel from resting point to this area and then back again and it's going to move back and forth a number of cycles.

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But this molecule is bumping in to its neighbor.

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I'll make this 1A green molecule, so it's bumping into this green one and now the green one is moving and then coming back.

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So we have a propagation or a movement of sound in this energy wave, a wave of disturbance across the medium.

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So there's one last video I'm going to put in in our folder.

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It links to a Khan Academy video about the production of sound.

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The Khan Academy videos go very quickly, so once you get it moving you can click a little gear at the bottom and slow down the pace to the video if you just want to take it a little bit slower.

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So we're going to stop our first week right here and get into some more properties of sound next week with Doctor Mosley.