Sound Waves In Liquids And Solids

by Patrick Ford
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Hey guys, we already saw the speed of sound in an ideal gas. Now we want to talk about the speed of sound specifically in liquids and solids, which are also elastic media, so they can also propagate sound waves. All right, let's get to it. As I said, sound can travel through any elastic medium, so we could also travel in liquids and solids. Alright, sound travel through a solid or liquid would look the same to sound. Traveling through gas. It would just have a different speed. Okay, the speed of sound in a liquid is equal to the square root of be divided by row, where B is known as the bulk module lists of the liquid and row is just the plain old density, the speed of sound in a thin solid. So something like a rod. If you were to put a little speaker with sound thing that sound propagated on the thin solid is gonna be the square root of why over row, where Roe is still just the plain old density, and why is known as the young's modu Elice of the solid. Okay, now, if you've covered elastic elasticity, then you've seen ma July before, If not what? A module ISS is of a solid or liquid is it's a measure of the elasticity of that substance. Okay, the larger the module iss, the harder it is to compress that material. Okay, so if you want to take a chunk of something and you want to squeeze it from all sides to a smaller chunk of that something, the larger the bulk module lists the mawr Force, you're gonna have to put on every surface. The more pressure you're gonna have to put on all the surfaces. Thio get it to change its volume. Okay for the young's modu Elice. If you have a rod, the larger the Youngs modulates, the harder you're gonna press on the end of the rod to reduce its length. Okay, the more pressure you're gonna have to apply on the end of the rod to reduce its length. Let's do an example. De ionized water has a bulk module list of 22 times 10 to the nine Pascal's. What is the wavelength of a 250 hertz sound wave in D I water? Okay, if we want to know the wavelength of some frequency we know that the speed relates the two. Okay, What's the speed of sound In de ionized water. Well, the speed is gonna be the bulk module ists divided by the density. The bulk modulates were told and the density of the water is just kg per cubic meter. But right, that's an S I units. And this whole thing is going to be 14 meters per 2nd 1483 m per second. So with wavelength is gonna be 83 divided by 250 hertz, which is 5.93 m of pretty large wavelength. But that's because sound is traveling so quickly. Okay, so it travels such a far such a far distance per unit time. Alright, guys, that wraps up our little discussion here on the speed of sound in liquids and solids. Thanks for watching