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Questions tagged [vibrations]

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106 questions with no upvoted or accepted answers
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6
votes
0answers
517 views

Physical meaning of Laplace-Beltrami eigenfunctions?

The eigenfunctions of Laplace-Beltrami operator are often used as the basis of functions defined on some manifolds. It seems that there is some kind of connection between eigen analysis of Laplace-...
5
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1answer
413 views

Energy Conservation of waves at a boundary

Consider a wave traveling on a string with velocity $\upsilon$ and mass density $\rho$ having unit length so that the mass of the string is $\rho$. Considering the string to be a simple harmonic ...
5
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2answers
1k views

What actually is the wavevector in the context of phonons and lattice vibration?

When we deal with Electromagnetic waves the wavevector has the meaning that it encodes the information about the direction of propagation, together with the wavelength. In Quantum Mechanics, the ...
3
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0answers
55 views

Prove from first principles that a guitar string will vibrate at a constant frequency

From experience I am aware that a taught string will generally vibrate with a constant frequency. I wanted to prove this by considering the relation of distance from the resting position, and its ...
3
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0answers
47 views

Can I compute mass of an object in a box based on the sound the object makes when shaken? (Barton Fink movie)

In this movie called "Barton Fink" the main character, Fink, is given a mysterious box with an object inside it, he shakes the box up and down, is it possible to calculate the mass of the object ...
3
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1answer
67 views

Vibrational modes of a black hole's event horizon

I understand that it is possible for the event horizon of a black hole to support damped modes of vibration called quasi-normal modes, in which it oscillates between spherical and and various oblate ...
3
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0answers
2k views

Chladni Plate Mathematics

I am a high school student doing an IB Extended Essay investigation concerning the resonant frequencies of Chladni plates of differing materials and sizes. Would someone please explain the definition ...
2
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0answers
17 views

Does putting a part under stress change its natural frequency?

It is easy to imagine how tension changes the natural frequency of a wire. Intuitively it happens with a guitar string when you bend the neck. However, does putting a beam under stress (internal or ...
2
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0answers
27 views

Physics of a catenary with sinusoidal motion at one end

If we have a catenary line with a mass per unit length of m with one end fixed and the other end moving in sinusoidal motion like $A.sin(\omega.t)$, how would I ...
2
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0answers
26 views

vibration and movement of electric appliance

So, what I am thinking about here is a cooking mixer placed into a bowl which is turned on and left moving on its own. The bowl is such that it does not topple nor the mixer falls out of it. Once the ...
2
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0answers
27 views

Book for electromagnetic waves and radiation

MIT course 8.03SC recommends Electromagnetic Vibrations Waves and Radiation (The MIT Press) by Bekefi and Barrett for extra reading however I am unable to find any soft copy online and its too costly ...
2
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1answer
193 views

Are acoustic phonons always the lowest energy vibrational modes in solids?

In solids with unit cells containing more than one atom, the normal modes show acoustic and optical branches. The number of optical branches is proportional to the number of atoms in the unit cell, ...
2
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1answer
114 views

How is temperature related to quantum vibrational states of molecules?

When a molecule of greenhouse gas absorbs a photon of long wave infrared radiation it is boosted to the next allowed vibrational state. The vibrational state, as I understand it, involves deformations ...
2
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0answers
150 views

Seismology - PPV / VDV from geophone waveform data

I'm using an inexpensive seismometer to try and measure the effects of local HGV traffic on buildings. The device is connected to a Raspberry PI that has a Cirrus Logic Audio Card. The signal is fed ...
2
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1answer
277 views

What is the difference between the dipole in IR and Raman vibrations?

In order for a vibration to be IR active, there must be a change in the dipole moment ($\mu$) of the molecule, which is given by: $\mu$ = $\sum$ q * r Where q is the charge magnitude and r is the ...
2
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0answers
478 views

What is the physics behind the vibrating feeling you get when you touched an inducted metal surface?

When I was last working on the highway, I stopped to help a motorist parked under high tension power lines. I'm driving a large Ford Transit van, fairly box shaped. My van was parked 90 degrees (...
2
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0answers
32 views

Trying to prove, that an initial spatial and restricted displacement on an infinite string, with a density discontinuity, will transmit AND reflect

This is a rather trivia problem, but I have been trying to prove it, since all of the Books I have read - online or not - take it for granted. The problem I'm talking about is "Vibration of String" ...
2
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0answers
45 views

Is LIGO designed as a bandpass instrument?

This question intended for those that may have personally worked on LIGO and are knowledgeable about its detailed systems architecture. I understand that LIGO basically uses a Michelson-Morley type ...
2
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1answer
42 views

Outbalancing vibrations

Consider a ship vibrating in the fundamental/principal/first symmetric mode shape (similar to that of a Bernoulli-Euler beam), induced by the main engine (similar to that of a vibration shaker). I ...
2
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1answer
104 views

How can frequency of waving in water change the direction an object on the surface goes?

In an Australian experiment the physicists studied effects of a simple object that causes waves in fluid. They found that if it vibrates slow, the objects on the surface move away from the source of ...
2
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0answers
44 views

Creating a structural dynamic model using only modal test data

Short version: Suppose I excite a vibrational response in some structure and measure its mode shapes and natural frequencies. Is it possible to create a structural dynamic model of the structure ...
2
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0answers
188 views

De-excitation and vibrational frequency

By utilising energetic beams of particles it is possible to set atomic nuclei into vibration. For a certain nucleus the subsequent de-excitation results in the emission of photons of energy $1$ $MeV$. ...
2
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0answers
560 views

Modal analysis with aerodynamic damping

I'm using modal decomposition to predict the steady state response of a beam structure to harmonic loading. The structure itself is very lightly damped, but we know from experiments that the ...
2
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1answer
345 views

Sound - for purposes of vibration

What is the best way to distribute noise from more than one source (I'm envisioning a system with many), within a dome, with the ground as its primary target, at optimal frequencies and volumes to ...
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0answers
17 views

Energy in a vibrating part of an engine

I have sensor data of the vibrations of the parts of an engine. I was wondering whether I could calculate how much energy a part contains in a given time window. Now the energy of a wave given by ...
1
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2answers
544 views

Difference between Oscillatory motion and vibratory motion

What is the difference between oscillatory motion and vibratory motion. I have read in my book that "If the amplitude of oscillatory motion is extremely small,the motion is called vibratory motion". ...
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0answers
30 views

Spring oscillation model

When a spring - in real world - is extended $Xo$ from its natural position, it oscillates and eventually decreasing it's amplitude with time, comes to a stop. Is this a damped system or no? If yes how ...
1
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1answer
69 views

Why are higher frequencies amplified less by filling a bottle with warmer water instead of colder water?

Out of curiosity I was trying to figure out what makes the sound of hot water versus cold water filling a bottle different, but I'm unable to find any explanation as to why such differences occur. ...
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0answers
59 views

Faraday waves and Chladni plates

I am a High school student who's writing a research paper about Faraday waves and Chladni plates. I've been doing a lot of research on Faraday waves specifically, as there aren't many sources that can ...
1
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0answers
71 views

sounds of polygonal ring chimes of metal

Suppose we have a number of rings, each of them is constructed from some mass of wrought iron or steel: each ring is a polygon, which I would like to suppose is constructed without welding (so they ...
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0answers
22 views

Error in FFT (Sectrum) analyzer Instrument

Recently I performed an experiment on finding the natural frequency of vertical cantilever. I used accelerometer and FFT analyzer instrument for measuring it. First I kept the accelerometer near the ...
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0answers
41 views

Laser creating weird patterns on screen when reflected from a vibrating membrane

Me and a few friends were doing an experiment today in which we took a membrane stretched over a speaker, and a small mirror in the center of the membrane. We reflected a laser off the mirror on a ...
1
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0answers
18 views

Different ressonant frequencies for velocity and displacement

For a damped oscilator, by working ou the math one can easily see that the ressonant frequency for the displacement is slightly lower than the one for velocity. But why? How we see this intuitively?
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54 views

Justification for using wave equation for describing a phenomena

I have recently started learning about waves. We didn't really formally describe what a wave is, but instead started by looking at a concrete example namely harmonic sinusoidal waves in 1d. We then ...
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0answers
32 views

Is using an IMU suitable for measuring the vibrations of the string?

I want to measure the vibrations of the guitar string. I've got an IMU sensor. I want to mount it on a string and measure the vibrations of the element. IMU: Sparkfun ITG3200 I'm not pretty sure is ...
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0answers
57 views

Assumed mode method to solve problems

I am trying to understand part 4 (Approximate analytical solution to pull-in voltage) of this paper, "An approximate analytical solution to the pull-in voltage of a micro bridge with an elastic ...
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0answers
44 views

Uniqueness of principle coordinates

I am currently studying two-degree of freedom systems in mechanical vibrations. I understand that in general, the equations of motion corresponding to the two independent coordinates can be coupled. ...
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0answers
76 views

Has the asymptotic theory of eigenvalues of infinite matrixes already been applied to vibrations analysis?

My question is reffering to the masses/springs model of a material, like the one presented in this article http://www.laserpablo.com/baseball/Kagan/UnderstandingCOR-v2.pdf. If one treates a long ...
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0answers
156 views

Where do air molecules move at the greatest speed in a sound wave?

In my lecture notes it states that The movement of the particles is greatest were the gas is rarefied. But I wold disagree. I would think that the speed of particles is exactly zero at the ...
1
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0answers
63 views

The lightest, stiffest, and largest panels available are made of what?

This document on audio exciters lays out some uncited requirements for the best sound from an excited panel: A stiffer panel will give better high frequency (treble) performance. A lighter panel will ...
1
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0answers
69 views

What's the effect called when vibrations move through a cable under tension?

I'm not sure how to describe it, but there is a certain sound of vibrations through a tensioned cable, you might hear it as sound effects in a movie where cables are snapping, some have described it ...
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0answers
56 views

What is Lamè mode?

I am trying to read some of the articles that says Lamè mode. But I can't find in google that describes Lamè mode. Can anyone quote good reference for this term?
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0answers
128 views

Is disturbance propagation velocity equal to wave velocity in a solid body?

How do the disturbance propagation velocity and wave propagation velocity relate to each other? To explain my question in details I will describe the following situation from the theory of acoustic ...
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0answers
360 views

What is the highest frequency for ripples on water

I want to transmit sound vibrations as ripples on water, as an experimental audio delay effect. Can I make ripples at audio frequencies, that will travel over about 10cm or more? How about other ...
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0answers
2k views

Is it possible to generate deep infrasound with subwoofer and a pipe?

I would like to check if infrasound noise can make people feel weird (as in a "haunted" house). Some people claim that noises of such frequency may be the cause of "paranormal" sensation in humans. ...
1
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0answers
312 views

Difference between three mutually complementary methods: Raman, Infra-red spectroscopy and inelastic incoherent neutron spectroscopy?

When I read the wiki on Raman spectroscopy, I found a paragraph explaining what system is suitable for using Raman and what others do not. It provide two other method as shown in title: infrared ...
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1answer
84 views

Energy corresponding to the peak of velocity power spectrum

I ran a MD simulation for a number of N molecular hydrogen. I used the velocity time history of system for each atom and subtract the velocity of center of mass of each molecule from the velocity of ...
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0answers
90 views

Models for vibrations and stress waves generated due to impact?

Say that a small metal ball impacts a long thin cylindrical rod from above (let's say height of around 10 cm) in an elastic collision and causes stress waves to propagate left and right from the point ...
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0answers
83 views

What is the effect of vibrations on an object's properties?

What do vibrations do to an object's properties? By making an object vibrate at a high frequency (compared to its static state) would vibrations: Increase or reduce its moment of inertia? Increase ...
1
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0answers
148 views

Non-linearity of a guitar pickup

I basically understand induction and why a pickup generates a signal. (From: http://www.brighthubengineering.com/consumer-appliances-electronics/64277-the-physics-behind-the-electric-guitar/) What ...