Amplitude Entrainment: Forum Q&A

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Discussion Overview

The discussion centers around the concept of amplitude entrainment and resonance in vibrating systems. Participants explore the idea that a stronger amplitude vibration may influence a weaker one, questioning the validity of this claim and its implications in physics.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant recalls that two similar vibrating bodies can achieve constructive interference but initially believed their amplitudes were independent.
  • Another participant mentions a claim that the higher amplitude body can influence the quieter body to adopt its amplitude, asking if this is correct and if it has a specific name.
  • Some participants express skepticism about the mechanism behind the claimed phenomenon, suggesting that resonance occurs when an oscillator is forced at its natural frequency.
  • A participant provides an example of a soprano breaking glass, linking it to the concept of resonance and amplitude growth over time.
  • There is a reference to a "Law of Resonance" as described by a friend of one participant, which states that weaker vibrations will change to match stronger ones upon encountering similar systems.
  • Another participant questions the existence of this principle in physics, noting difficulty in finding references to it in research.
  • One participant suggests that the term "entrainment" is more commonly associated with biology, particularly in the context of circadian rhythms.
  • Another participant asserts that there is no known physical law supporting the idea that a weaker oscillator takes on the characteristics of a stronger one, emphasizing that resonance is not the same as the described phenomenon.
  • It is noted that effects similar to those described could occur in nonlinear systems, where natural frequency might depend on amplitude, but this is often negligible in real-world systems.

Areas of Agreement / Disagreement

Participants express differing views on the validity of the claim that amplitude can be entrained between oscillators. There is no consensus on whether such a principle exists in physics, with some participants disputing the terminology and concepts involved.

Contextual Notes

Participants highlight the complexity of resonance and amplitude interactions, noting that real-world systems often exhibit nonlinearity, which may affect the outcomes discussed. The lack of clear examples or definitions contributes to the uncertainty in the discussion.

phanie12.geo
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I am so happy to have found this forum. I am trying to understand a concept about frequency entrainment. I remember reading many times that two different, but similar vibrating bodies can lock into a constructive interference regarding their frequencies, however I thought that their amplitudes were completely independent of that.

However recently, a self proclaimed physics affcianado told me that when two similar vibrating bodies come into contact, the higher amplitude vibrating body will cause the more “quiet” vibrating body to take on its amplitude. In other words, the louder vibration wins. Is this correct? If so, is there a name for this phenom?
 
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In doing some online research I found this image that essentially explains what my friend is saying. http://www.flickr.com/photos/44173456@N03/4734783316/"

What do you think? Is it bunk?
 
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No info on this?
 
Never heard about that, and I can't think of any mechanism to give you that phenomenon. You can have resonance if you force an oscillator with its natural frequency, of course. Maybe you're talking about that. Can you give a more physical example?
 
I really can't give an example becasue this is all he told me. I was confused by it.

jrlaguna said:
You can have resonance if you force an oscillator with its natural frequency, of course.

Can you explain this a bit more please?
 
The soprano lady who can break glasses with her voice... All oscillators have a natural frequency, at which they will oscillate if perturbed and then left alone. Now, if you force an oscillator with its natural frequency, its amplitude will grow with time (and eventually may break up, like the glass). This can be achieved if you have a second oscillator with the same frequency, which is oscillating by itself, but which is somehow linked to the first one.
 
Ah yes! Thank you. Do you have a link or book you can recommend where I can do some more reading on this specific subject?
 
There is a chapter in first volume of Feynman's lectures on physics (all praise be given to him) ;) , that's quite nice. Of course, just typing "Resonance" in wikipedia or google can give you lots of info.
 
OK, I will get a copy of that book.

Here's an email I received from him regarding this "Law of Resonance" when I asked for an example. Its not really an example, but he explained a bit more. I am not finding this anywhere in my own research regarding the science of physics:

"When one system encounters another similar system, their vibrations must come into a state of resonance (harmonic vibration). This law also states that the weaker amplitude vibration will be influenced by and change to match the stronger amplitude vibration."
 
  • #10
phanie12.geo said:
OK, I will get a copy of that book.
"When one system encounters another similar system, their vibrations must come into a state of resonance (harmonic vibration). This law also states that the weaker amplitude vibration will be influenced by and change to match the stronger amplitude vibration."

Is this a principle of physics found anywhere? I have searched quite a bit and am not finding it. TIA!
 
  • #11
How about the Principle of Entrainment? Can someone state it for me?
 
  • #12
This use of the term 'entrainment' is about circadian rhythms and really belongs in the biology section, which may be why you have seen almost no takers.

I am not a biology specialist so cannot help further.
 
  • #13
So this does not occur on physics at all?
 
  • #14
There is no physical law that I am aware of whereby two oscillating systems come into contact with one another and the weaker oscillator takes on the characteristics of the stronger oscillator. There isn't even any guarantee that they would constructively interact.

Perhaps your friend is using the wrong terminology or just generally doesn't know what he is talking about?

Resonance occurs - all the time. However, resonance is not what you are describing. it could be that your friend is thinking of resonance and just doesn't understand it as well as he thinks he does.
 
  • #15
Effects like this can occur in nonlinear systems, where the natural frequency depends on the amplitude of vibration for some reason.

Every real-world system is nonlinear to some extent, though the nonlinearity is often small enough to be ignorable.

But the graph you posted could be nothing more than forced response of a linear system. In other words, some energy from the "large" oscillator is getting into the "small" system and shaking it around at the same frequency, once the the initial transient response (at a slightly different frequency) has died away. It's hard to give any "explanation" for it without knowing what system (either physical or mathematical) the graph is showing the response of.
 

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