Particle displacement vs time graph of sound. How can this happen?

In summary, In an ideal gas, pressure is proportional to density, when the temperature is kept constant.
  • #1
sameeralord
662
3
Hello everyone :smile: ,

I'm so confused with particle displacement vs time graph and pressure vs time graph of sound. I thought maximum displacement of a particle is its compression and minimum displacement is its rarefaction. For some strange reason the graphs show exactly the opposite. How can the particles be at atmospheric pressure when the displacement is maximum. Your help would be greatly appreciated. Thanks :smile:

sound-graphs.jpg
 
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  • #2
You need to understand how to read the displacement graph. If there were no sound wave, there would be undisturbed particles at every point x. The displacement at coordinate x tells you the displacement of the particles whose undisturbed position is at x. Thus if the displacement is a maximum at point x, it means that the particles that usually reside at point x have been displaced to the right (positive direction); If the displacement is a minimum, it means they've been displaced to the left. Thus the position where the pressure is maximum would be between a maximum and minimum of displacement. Make sense?
 
  • #3
Note that in an ideal gas, pressure is proportional to density, when the temperature is kept constant.

Looking at your displacement graph, the molecules that are normally at x = 0 have moved to the right (+x direction), and the molecules that are normally at x = 18 have moved to the left. So in the region between x = 0 and x = 18, the density of the gas is higher than normal, and so is the pressure.
 
  • #4
Thanks both of you for your replies :wink: They were both very helpful!

That was a great response jtbell I think I got it. Is it when particles move right and then particle further move left high pressure region is caused meaning compression and vise versa for rarefaction.

However as I just realized this is a displacement distance of wave graph. However my graph in my notes is identical but it has time in the axis. This is the closest pic I found in the interent. It is basically the same graph but with time in the x axis. I don't think it would make a difference. Would it? If that is so I got it :cool:

Thanks again for your replies! :cool:
 
  • #5
This information is really very helpful ... thanks :D
 
  • #6
Hello there!
I understood in part what you have said here. But how can compression and rarefaction regions correpond to zero particle displacement?
 
  • #7
Nevermind, I got it :)
Thank you anyway!
 

1. What is a particle displacement vs time graph of sound?

A particle displacement vs time graph of sound is a visual representation of the movement of particles in a medium (such as air) over time as a sound wave passes through it. It shows the displacement of the particles from their original position as the sound wave travels through the medium.

2. How is a particle displacement vs time graph of sound created?

A particle displacement vs time graph of sound is created by using a device called a microphone to measure the changes in air pressure caused by a sound wave. The microphone converts these changes into an electrical signal, which is then graphed over time to create the displacement vs time graph.

3. What does the shape of a particle displacement vs time graph of sound indicate?

The shape of a particle displacement vs time graph of sound can indicate several characteristics of the sound wave, including its amplitude (loudness) and frequency (pitch). A larger amplitude will result in a taller graph, while a higher frequency will result in a graph with more closely spaced peaks.

4. How can a particle displacement vs time graph of sound show the speed of sound?

The speed of sound can be determined from a particle displacement vs time graph by measuring the distance between two consecutive peaks (representing one full wavelength) and dividing it by the time it takes for the sound wave to travel that distance. This calculation will give the speed of the sound wave in the medium.

5. Can a particle displacement vs time graph of sound show the direction of sound?

No, a particle displacement vs time graph of sound cannot show the direction of sound. This graph only represents the displacement of particles in a medium, not the direction of their movement. To determine the direction of sound, other methods such as triangulation or using multiple microphones are needed.

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