Hey /sci/ I'm trying to develop a theory on what happens to things like sound waves after they "die." I haven't found any current theories on what happens to them after they're created other than they simply cease to exist. But I think something much different. I may just be talking nonsense, but does anyone know any current standing theories about what happens to sound after it "dies?"
No I think that it's initial energy level can no longer sustain an actual sound wave and the particles- Wait I don't wanna actually tell you guys, because I've already started thinking up possible equations and such for this concept.
true, maybe think in terms of still water and adding a rock creating a ripple, notice the ripple continues until it is broken up with other things around it, but if there was a giant body of still water, would the ripple continue forever until the kinetic energy was used up?
The ripples of water are still water. The only thing being lost is energy but the water is still there and can still create ripples if energy is given. Kind of picture this same concept with sound... Sort of...
>No I think that it's initial energy level can no longer sustain an actual sound wave and the particles
Um, before you dive into acoustics and wave theory I think you should start at basic physics like conservation of momentum and energy.
Work your way up to the wave equation from there.
No no see, after the sound wave uses up all of its initial energy is what I'm trying to figure out. I'm trying to disprove the theory that sound waves just up and die after they're created. I think it's much more than that. Are there any more standing theories that already exist about what happens to them?
There's no mystery, the energy is dissipated into other forms.
Specifically it can be modeled as a damped oscillation (timewise). Spatially it becomes more complicated but there is no super spooky trickery going on. It's just entropy.
>Are there any more standing theories that already exist about what happens to them?
Yes, friction and viscosity work against the propagation of the waves and energy is converted from kinetic energy to thermal energy. This is irreversible, so you can't get the sound back.
I highly suggest reading up on the laws of thermodynamics.
No but phonons will explain the same thing. It's all related.
You cannot escape the conservation of energy for starters. Energy is always conserved. And if you are trying to convert energy from one form to another you cannot escape entropy. It is the way the universe works.
Alright, well, I'm done after this, but no you're wrong.
There is no initial energy needed for this conversion, it's the path of least resistance. Sound waves are fluctuations of pressure (or density if you like to think of it that way) that propagate through a medium, usually a gas.
By fluid mechanics alone this is a viscous process and that will damp out the amplitude of the waves as described here>>7650009. Combine that with the inverse square law and you have an initial energy that has now spread out over a large volume as well as being damped by viscosity in the medium it propagates.
TL;DR your wave spreads out, gets damped by viscosity, and its energy gets turned into heat. Tiny, tiny amounts of heat, but heat none the less. This is very, very well studied. Good night.
So by that logic, the remaining energy that sound has left after entropy is converted into heat? I'll have to look into that a bit more. But thank you very much for your time, Anon.
No no, there IS initial energy, in the beginning when it's created. But it gradually loses it over time. So with that logic. How could it possibly create heat if that were the case?
This is like waves 101 shit.
The directed energy of the sound waves gets converted into stochastic kinetic energy (heat).
The waves also spread out as they travel, until their energy density is below the noise floor.
Sound is a mechanical wave which requires a medium. That's why there is no sound in space since there is no medium. Sound waves uses air as a medium in Earth's atmosphere and ripples the air particles that the receptors in your ears pick up. The sound doesn’t 'die', it disperses and eventually absorbed by an object thus conserving momentum.