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

[scilearner]

Hello everyone ,

 

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

 

[Kyrisch]

Well the first problem is that these graphs are not versus time. They are versus position along the wave in centimeters.

[swansont]

At maximum and minimum compression the particles aren't moving — they move due to a pressure difference.

[scilearner]

Thanks both of you for your replies Oh I didn't realized the that it is not against time. However in my notes there is exactly the same graph but the displacement graph has time in the x axis . This is the closest pic I found in the internet. So treat the x axis as time and explain. Thank you

[Kyrisch]

Well, given that the speed of propagation of the wave is constant, the graphs of versus position and versus time should be identical, I was just pointing that out.

 

As for explanation, swansont pretty much covered it. Do you have any specific other questions?