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# Relative speed of sound in solids, liquids, and gases

Sounds travels at different speeds in different media. Created by David SantoPietro.

## Want to join the conversation?

• What exactly is the Bulk's modulus? I understand that it is a measure of rigidity, but how do we define rigidity? Is there a formula? What's the difference between rigidity and pressure if both of them are measured in Pascals?
• Please explain how echoes are formed - and how the angle of incidence is equal to the angle of reflection and why only sometimes you can hear echoes and sometimes you can't. Then also the calculations to figure out how far you are from a sound reflective surface (e.g. how steep a cliff is)
• When a sound wave meets a change in medium, it splits. Some of it goes through, some is reflected back. Your brain is weird sometimes. If you hear 2 similar sounds in a small interval of time, your brain will hear them as just 1 sound.
For you to notice the echo, the wall reflecting the wave back has to be far enough way so that it takes more time for the wave to go and come back, enough for your brain to listen 2 different sounds.

As for the angles, it's very hard to explain it in words. I made a program that simulates a similar behavior for light, which works in the same way sounds does in regards to reflections. Try it out: https://www.khanacademy.org/computer-programming/light-reflection-and-refraction/5872552844722176

Hope it helps :D
• What about hot humid air? Would the speed of sound be faster or slower than room temperature, non humid air?
• As the humidity increases, the speed of sound will increase.
• Why is it so that light, an electromagnetic transverse wave slows down in denser medium but sound, a mechanical transverse wave travels faster in a denser medium??
• They are totally different types of waves. There's no reason to expect an electromagnetic wave that requires no medium to behave the same as a mechanical wave that does require a medium.
• Does density matter? My textbook, College Physics - a strategic approach by Knight/Jones/Field, states, "The speed of sound doesn't depend on the pressure or the density of the gas" on page 474 in chapter 15 on Traveling Waves and Sound. Who's right - Khan or Knight?
• We know that sound energy can travel through gases and solids. Then why does it gets reflected by walls and does not pass through it?
• Some of it gets reflected just like how when a water wave reaches land some of the water gets reflected back to the center of the waves. So you might be able to hear a small echo. But some passes through just like how some water in a water wave flows or splashes onto the upper surface of the land and gets absorbed and some of the land in the deeper parts of the body of water absorb the water that travels in waves. When it passes through just like how you or nature can change the speed of the water waves, the sound speeds up. However because of how some gets reflected in the solid which makes the molecules in the solid vibrate against each other more it produces heat instead of an echo. This dampens the vibrations so speed increases and amplitude decreases and then speed decreases again but the amplitude doesn't change. So you can hear what is going on next door to your house because of how the sound passes through room temperature air and then their walls and then outside temperature air and then your walls and then room temperature air again and into your ears. However because of dampening it is much quieter where you are then it is where the sound source is and not just a little bit quieter because of distance.
• Why exactly sounds waves are after in denser materials? I thought the more numerous of molecules per metre cubic will "help" waves propagate..
• This has more to do with the interaction of macroscopic mechanical properties of the material being considered. Sound waves propogate via vibration of the medium, provoking an interaction between bulk material constants such as lame's constant, elasticity modulus, poisson's ratios, and density. A quick search on dilatational wave speed will show increasing density decreases wave propagation speed.
• Does the formula mentioned in this video have a title?
• It's not Newton- Laplace equation .its only Newtons equation because Newton Laplace equation has a "gamma" in the numerator called Adiabatic elasticity n moreover the equation given in the video is applicable only at constant temperature(isothermal) and that of Newton Laplace equation is applicable at Adiabatic conditions ..
• Isn't it not density which makes the speed of sound faster ?
(1 vote)
• It's not only density. It also can involve a metric called the bulk modulus, which is related to density, for a gas. And for a solid or liquid it also involves something called the shear modulus.