Understanding Sound Wave Amplitude in the Equation s=Sm cos(kx-wt)

[elabed haidar]

i have a question about sound waves :
we know that the equation of sound wave can be written in the form s=Sm cos(kx-wt)
,but i still don't get the meaning of Sm .I know that in the transverse wave ingeneral , and in particular the string the maximum amplitude is how much the string can go vertically upward ,
so what about the maximum amplitude in sound wave?
PS the defintion of sound wave amplitude is the maximum postion of the element at equilibrium ?

 

[tiny-tim]

hi elabed haidar!

as you know, s is displacement and s_m is maximum displacement …

the displacement here is the distance any particular particle goes from its own equilibrium position …

in a transverse wave it goes up or down, and in a spring (or sound wave) it goes forward and backward

PS the defintion of sound wave amplitude is the maximum postion of the element at equilibrium ?

you mean the maximum postion of the element from its equilibrium position?

yes, the maximum distance forward or backward ​

 

[elabed haidar]

i still don't get it can you please illustrate more please?

 

[elabed haidar]

here is the problem i understand it in a spring Xm but in a sound wave i still don't get it

 

[elabed haidar]

one more thing in sound wave resonance why when we have tube which is one open from only one side the resonant frequency f=nv/4 lamda ?? and thank you very much professor

 

[tiny-tim]

for pictures, google "longitudinal wave" and click "Images"

 

[seonshrestha]

why does longitudinal waves can propagate through solid, liquid and gas? and not transverse except in solid?

 

[chrisbaird]

Sound waves are pressure waves, so the picture of a longitudinal wave going down a spring is not always helpful. The amplitude of the sound wave is the maximum local air pressure reached when the wave traverses through it. So a sound wave with a higher amplitude (a louder sound) will have higher pressure. http://www.dailymotion.com/video/x6bz5x_plane-breaks-sound-barrier-then-exp_tech"

 

[Trevormbarker]

one more thing in sound wave resonance why when we have tube which is one open from only one side the resonant frequency f=nv/4 lamda ?? and thank you very much professor

Because the open end will have an antinode at it and you can't just have any wavelength because antinodes occur periodically

 

[seonshrestha]

Sound waves are pressure waves, so the picture of a longitudinal wave going down a spring is not always helpful. The amplitude of the sound wave is the maximum local air pressure reached when the wave traverses through it. So a sound wave with a higher amplitude (a louder sound) will have higher pressure. http://www.dailymotion.com/video/x6bz5x_plane-breaks-sound-barrier-then-exp_tech"

but how does mechanical longitudinal wave travel in solid, liquid and gas medium? and transverse mechanical wave (such as in rope)travels only in solid medium?

 

[olivermsun]

but how does mechanical longitudinal wave travel in solid, liquid and gas medium? and transverse mechanical wave (such as in rope)travels only in solid medium?

See the other thread: https://www.physicsforums.com/showthread.php?t=496932.