Questions tagged [vibrations]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
1 vote
0 answers
20 views

The definitions of coherent phonons and acoustic phonons

I found that the definition of coherent phonon: A femtosecond laser pulse can initiate collective, in-phase atomic motions in solids called coherent phonons. My question is: what is the difference ...
MathJacky's user avatar
1 vote
0 answers
23 views

Can someone please explain how is the setup stated below apparently causing amplitude resonance in spite of different frequencies?

Suppose I have a pendulum such that its natural frequency is $2 Hz$. I release it from One extreme by striking it with a tuning fork of frequency $1 Hz$. Now in $0.5s$, the pendulum will undergo 1 ...
Shirshayu Sarkar's user avatar
1 vote
0 answers
17 views

Are Harmonic or Subharmonic resonance the only outcomes for a system with applied vibrations?

I'm working on performing a linear stability analysis on a system with fluid undergoing applied vibrations. Now, usually these systems are analyzed with no fluid velocity. Under these conditions, it ...
Daniel Harper's user avatar
0 votes
0 answers
26 views

Phonon eigenfrequencies under time reversal

In G. P. Srivastava's "The Physics of Phonons", 1e., the ansatz which solves Newton's second law in the harmonic approximation is taken to be $$ u_\alpha(\ell b;t) =\frac{1}{\sqrt{m_b}}\...
CW279's user avatar
  • 215
1 vote
1 answer
65 views

How to interpret huge number of phonons?

In my condensed matter class we have seen how to treat the problem of vibration in a lattice in quantum mechanics. After heavy calculation we derive that the number of phonons with a given crystal ...
CoolerThanACooler's user avatar
0 votes
0 answers
30 views

What is happening to the air pressure in an extremely high-intensity low-frequency sound wave e.g. 30 Hz at 100 dB?

I'm doing research on low-frequency sound in music and one text states 'High-sound pressure levels condense air – noticeably thickening it, making it feel heavier.' Is this true and what does that ...
Spectre's user avatar
2 votes
1 answer
65 views

Anharmonic effects in crystals, help with intuition

I've been reading a bit about how it is necessary to consider anharmonic effects in crystals if one wants to properly understand things like thermal expansion etc. So for example here: So the cubic ...
JPP's user avatar
  • 23
0 votes
1 answer
46 views

Modes of vibration

I've been thinking that 'modes of vibration' refers to the frequencies which produce standing waves in a system. But now I'm confused, because ChatGPT gave me the below response for my question. ...
Vivek karunakaran's user avatar
23 votes
4 answers
3k views

Magnetic field changes induced by vibrating electric guitar string

Here is a picture (from a paper by Feinberg and Yang in the Journal of the Acoustical Society of America) of an electric guitar string vibrating (mostly in the $y$ dimension) near a permanent magnet. ...
Wandering Logic's user avatar
2 votes
1 answer
23 views

Calculating vibrational mode coefficients of a drum for an arbitrary excitation

I am interested in the modes of a rectangular drum of size WxL that is fixed on 4 edges. The differential equation that governs the vibrations of a 2D membrane is $\nabla^2 \phi - \frac{1}{c^2}\frac{\...
Gappy Hilmore's user avatar
0 votes
0 answers
16 views

How to find the amplitude of the membrane of the speaker if the the input voltage is known?

Can anyone tell me what are the relevant pieces of information that are required to find the amplitude of a speaker membrane for a particular input ac signal frequency and voltage amplitude? Could you ...
C Ray's user avatar
  • 3
0 votes
1 answer
32 views

Do vibrational frequencies produced from sound pass through your entire body? from one side to another? [closed]

when there is a noise by me, i feel the vibration on my skin from the direction it’s coming, it moves into my body. a wall of what sound would feel like passing through me. i perceive it as container ...
na.arah's user avatar
0 votes
1 answer
73 views

Fourier transform for diagonalizing the Hamiltonian of lattice

I am reading the first chapter of "Statistical Theory of Fields" by Kardar. There he discussed the idea of phonons. Consider an ideal lattice at zero temperature with lattice vectors $\vec q^...
Iti's user avatar
  • 366
2 votes
1 answer
116 views

Sum of incident and reflected waves being the transmitted waves amplitude

Suppose we have an incident wave $\psi_i$ heading towards an interface, then when it reaches the interface it is split into a reflected and a transmitted wave: $$ \psi_i \to \psi_r + \psi_t $$ Why ...
jay53892's user avatar
0 votes
1 answer
44 views

Coupled pendulum question about equations of motion [closed]

I am working on problem number 2.3 of the Franklin, Powell, Naemi book Feedback Control of Dynamic Systems. The problem uses the simple coupled pendulum system below, where the two pendulum masses are ...
krishnab's user avatar
  • 181
0 votes
0 answers
20 views

Why do vibration MEMS gyroscopes need two oscillating modes?

Everywhere I look, I see that MEMS gyroscopes need to have two modes, that are orthogonal in direction. However, that puts a lot of significance to the detuning of these modes, and calls for highly ...
Rav's user avatar
  • 11
0 votes
0 answers
33 views

Linear Triatomic Molecule Bending Vibration Modes

In the Oscillations chapter of Goldstein Poole and Safko (3E, Ch 6), there is a discussion of the symmetric linear triatomic molecule (classical model, obviously). Initially, the 3 longitudinal modes ...
Poisson Aerohead's user avatar
1 vote
1 answer
162 views

What exactly are sympathetic vibrations?

On every source and in every example, it seems that sympathetic vibrations are quite directly linked to or are the same as resonance. The classic example of sympathetic vibrations is of two similar ...
Kayen Jain's user avatar
1 vote
1 answer
67 views

How to test resonance frequency of spring using sound?

I've done experiment with spring and mass to determine the natural frequencies of 4 springs. The first experiment went well but I had some problem when I want to test the resonant frequency. I'll ...
Rizky Aiman's user avatar
1 vote
0 answers
59 views

How would you experimentally determine the damping coefficient of a system?

We have a suspended beam that we need to determine the natural frequency, and more importantly the damping, of. To avoid resonance. The geometry of the beam is a little too complex to rely on theory ...
BoddTaxter's user avatar
  • 2,828
0 votes
2 answers
56 views

Does vibrational energy transfer to translational energy when an excited $\rm CO_2$ molecule collides with an $\rm N_2$ or $\rm O_2$ molecule?

My understanding is that when a $\rm CO_2$ molecule absorbs a photon of heat in the atmosphere after some time it simply re-emits that photon in a random direction. If that photon makes it back to its ...
Michael D Mays's user avatar
2 votes
2 answers
70 views

Exciton-phonon coupling Hamiltonian

I'm reading this article about coherent exciton transport in photosynthetic light harvesting and the role of quantized vibrations. Along the way, I came across a section where the article claimed the ...
slithy_tove's user avatar
1 vote
1 answer
55 views

"Spherical wave" in a 2D square lattice of masses and springs

Assume a 2D square array of masses with mass $m$ connected by springs with constant $\kappa$. Then the equation of motion for small perturbations in the plane of the array to the mass at $(l,n)$ is $$ ...
JonTrav1's user avatar
  • 930
2 votes
0 answers
24 views

Birefringince in 2D array of masses and springs

Assume a 2D square array of masses with mass $m$ connected by springs with constant $\kappa$. Then the equation of motion for small perturbations in the plane of the array to the mass at $(l,n)$ is $$ ...
JonTrav1's user avatar
  • 930
1 vote
2 answers
76 views

Vibrational spectroscopy energy spectrum

I have a question regarding vibrational spectroscopy. In vibrational spectroscopy we are describing the vibration of molecules with the Morse potential which gives us stationary wavefunctions that ...
Silas's user avatar
  • 480
1 vote
1 answer
52 views

Why is an ultrasonic transducer able to send energy into a tank without an opposing surface?

The diagram shows an ultrasonic transducer stuck to the bottom of an ultrasonic cleaning tank full of water/detergent. It's not supported at the opposing end - just hanging off the bottom of the tank. ...
Oliver Walters's user avatar
0 votes
1 answer
91 views

Source term and potential term in wave equation

I have often seen the wave equation as: $\Box \psi(x_1,x_2,x_3) + V(x_1,x_2,x_3)\psi(x_1,x_2,x_3) = S$; where $V$ represents the potential term ans $S$ represents the source term. I want to know that ...
SCh's user avatar
  • 652
0 votes
1 answer
184 views

Calculation of normal frequencies of a normal mode

In the Classical mechanics book by Goldstein, it is stated that if one wants to find the normal frequencies of a system, $\omega$ then the following equation has to be solved: $\left|\hat{V}-\omega^2\...
SCh's user avatar
  • 652
0 votes
0 answers
31 views

Underdamped and overdamped molecular vibrations

I am reading about the interactions between excitons and phonons in this article, and I came across the following equation for the underdamped component of the spectral density of the vibrational bath:...
slithy_tove's user avatar
0 votes
1 answer
64 views

Energy of polyatomic molecular vibrations

I understand that the energies of a simple diatomic molecular vibration are equal to $E_n=(n+\frac12)\hbar\omega$, and I also know the accompanying eigenfunctions for these energies. I have also heard ...
slithy_tove's user avatar
0 votes
0 answers
9 views

Seeking resources on mass-sensitive vibration modes for structures

I recently came across the topic of mass-sensitive vibration modes for structures in a research paper, but I have not been able to find many other resources on this topic. I am particularly interested ...
7 votes
2 answers
785 views

Energy of molecular vibrations

I have just read that the energy of a molecular vibration with frequency $\omega$ has eigenvalues of $(n+\frac12)\hbar\omega$, where $n$ is the quantum number. However, this equation really surprises ...
slithy_tove's user avatar
0 votes
3 answers
126 views

Eliminating sound vibrations by using destructive interference for sound waves

Can you eliminate sound vibration (when either it is audible sound, ultrasound or infrasound) by creating a destructive interference, but when both sources are in opposite sides? Say, you have one ...
lement's user avatar
  • 1
0 votes
2 answers
65 views

What do we mean by 'resonance frequency' of a system?

Whenever we talk about oscillations, we generally take the term 'resonant frequency' for granted, but I don't understand what this frequency depends on. For example, if we talk about a freely ...
Lime's user avatar
  • 87
0 votes
0 answers
38 views

FFT plot not aligning with lower natural frequencies

I have a cantilever beam with gapped springs on top and bottom and an impulse is given at the free end initially. I modelled it using finite element method with 30 elements. The beam then oscillates ...
john wick's user avatar
0 votes
0 answers
153 views

Multiple Pendulums and Resonance

Set up with multiple pendulums suspended from a connecting string. Pendulums 1 and 4 have the same lengths and hence, the same natural frequencies. Others(pendulums 2, 3 and 5) are of varying ...
Kayen Jain's user avatar
0 votes
2 answers
788 views

Vibrating membrane tension per unit length

I have been working on the problem of a vibrating membrane, with all the assumptions to make it ideal, but I still can't figure out why the tension per unit length multiply like that: if $T$ is the ...
AmadoC's user avatar
  • 103
3 votes
2 answers
387 views

How is maximum amplitude of resonance achieved?

Lets take a simplest case of a narrowly tuned system and the outside force exactly at the natural frequency of it. The first pulse will go through, bounce back somewhat weaker and get reinforced by ...
Dimitri's user avatar
  • 185
0 votes
0 answers
23 views

What are the best intuitive books to learn in-depth about waves and oscillations? [duplicate]

I was looking for a book/s that does not necessarily use a textbook-esque approach (e.g just providing definitions, equations, and examples) but dives deeply into the philosophy behind their mechanism,...
0 votes
1 answer
250 views

How to find Shear Force and Bending Moment in Finite Element Method for a cantilever beam with many elements

I have a cantilever beam with lots of elements. I am trying to find the sheer force and bending moment diagrams of the beam. EVERY SINGLE TUTORIAL AND EXAMPLE I SAW ONLINE SHOWS HOW TO DO IT FOR A ...
john wick's user avatar
1 vote
2 answers
37 views

Motorcycle handle Bar vibration & Bar End Weights

Pic 1 is a normal motorcycle bar end weights. My question, if I replace the bar end weights with a long threaded rod (M8x150) and the thread rod is inserted inside the handle bar(pic 2), will it ...
yus mulyo's user avatar
0 votes
0 answers
29 views

Transverse Vibrations of a Cantilever beam. Why does the % change in nth natural frequency increases with n in this case?

This is the problem in detail I have a cantilever beam. Now I am making it stand upright and adding water for different heights of SUBMERGENCE I am doing this by adding an ADDED MASS term from the ...
john wick's user avatar
0 votes
1 answer
56 views

Parameters which affect the transmission strength of a signal (vibrations) in a solid?

I'm working on a pair of devices - a signal injector and a matched detector for vibrations in solids. My background is not in acoustics, so I'm looking for pointers on what are the parameters that ...
Nick S.'s user avatar
0 votes
1 answer
39 views

Condition for true periodicity

In Vibrations and Waves, French writes that The condition for any sort of true periodicity in the combined motion is that the period of the component motions be commensurable- i.e., there exist two ...
GedankenExperimentalist's user avatar
-1 votes
1 answer
45 views

Is vibratory motion in straight line also pure translatory motion?

I think pure translatory motion is defined as change in position of the object such that the velocity of each particle of the object is parallel and in the same direction to each other and is of the ...
hsdfasd's user avatar
  • 31
1 vote
0 answers
51 views

Phonon modes and atom vibrations vs temperature

My understanding is that number of phonon modes depends on the number of atoms in a system and will be gradually populated with increasing temperature until Debye temperature. At the same time, atoms ...
user's user avatar
  • 11
0 votes
2 answers
82 views

Choosing a Complex Trial Solution for a Forced Vibration Problem and Expressing The Driving Force in Complex Terms

When solving forced vibration problems I would always choose a trial solution for the particular (stead-state) case in the form $x(t) = A \cos{\omega t} + B \sin{\omega t} $, but reading some books I ...
Iuri's user avatar
  • 3
0 votes
0 answers
35 views

How do you Determine the Fastest Vibrational Mode of a Crystal?

I understand that a crystal's vibrational modes are Phonons and have a minimum wavelength that is limited by twice the equilibrium separation between neighbouring atoms. But I don't understand how you ...
Connor's user avatar
  • 375
1 vote
1 answer
60 views

How to know if the vibration system requires one degree of freedom or two? and how to pick the right coordinate to describe the movement?

I want to know a trick that helps me understand oscillatory systems and how to pick the correct general coordinates that describe the movement, I tried everything but I still can't get the solution ...
I.ham's user avatar
  • 11
1 vote
0 answers
20 views

String vibration under periodic boundry conditions

I wish to known which are the vibration modes (in case that they exist) of an string vibrating under periodical boundary conditions (PBC). The question is related to molecular dynamics simulations of ...
user1420303's user avatar

1
2 3 4 5
13