# Tag Info

## Hot answers tagged vibration

373

So, I decided to try it out. I used Audacity to record ~5 seconds of sound that resulted when I dropped a penny, nickel, dime and quarter onto my table, each 10 times. I then computed the power spectral density of the sound and obtained the following results: I also recorded 5 seconds of me not dropping a coin 10 times to get a background measurement. ...

146

If you have the dimensions and material of an object, you can compute both the mass and the normal vibration modes. Just the mass is not enough - a large paper "coin" will have a different fundamental frequency than a small tungsten sphere. A summary of everything that comes below - the result of several edits, and including a nice interaction with the ...

52

If there were only one prong (imagine holding a metal rod in your hand), then the oscillation energy of the prong would quickly be dissipated by its contact with your hand. On the other hand, a fork with two prongs oscillates in such a way that the point of contact with your hand does not move much due to the oscillation of the fork. This causes the ...

43

I am by no means an expert in tuning fork design, but here are some physical considerations: Different designs may have different "purities," but don't take this too far. It is certainly possible to tune to something not a pure tone; after all, orchestras usually tune to instruments, not tuning forks. Whatever mode(s) you want to excite, you don't want to ...

17

Q. How do two coupled vibrating prongs isolate a single frequency? howstuffworks.com has an article on How Tuning Forks Work The way a tuning fork's vibrations interact with the surrounding air is what causes sound to form. When a tuning fork's tines are moving away from one another, it pushes surrounding air molecules together, forming small, ...

17

This is not an advertisement. Under the rubric of "do try this at home", I wanted to share one more thing that I discovered after writing my previous answer - but it is so unrelated to that answer that I thought it better to write this as a separate post. I discovered two interesting things. First, when you spin a coin on a hard surface, it "rings" with ...

10

The analogy is a very good one, because heat transfer is in fact modelled by phonons, which you could also use to describe sound waves. The crucial difference is that sound waves have a much longer wavelength (at least in the range of some millimetres) than thermal phonons (not more than a few orders of magnitude bigger than the atomic lattice scale). These ...

8

What do you think a $\Delta^+$ or $\Delta^0$ is, if not an excited nucleon? (To be sure the $^{++}$ and $^{-}$ states do not correspond directly to a nucleon, because there is no allowed lower spin state with that valence content.) The thing I am not sure about is how closely these excitation match the ones you are envisioning. They match nuclear excitation ...

7

Sound waves do generate changes in temperature because the propagation of sound is an approximately isentropic process. Keep in mind though that changes in static temperature can very well occur without the generation of heat. Moreover, the pressure changes associated with sound waves are of such a small magnitude that the observable temperature changes are ...

7

The forces on the screw are not symmetric. Once the screw is no longer turning loosely in the hole tightening the screw compresses the two materials held together (i.e. increases the stress on the material, i.e. stores energy in the material), while loosening reduced the compression (i.e. releases the stress). So a random dislocation will be more likely to ...

6

looking at the link you gave, I think it is just a problem of name convention and has nothing to do with oversimplifications. It was indeed ruled out that the reason of the failure was not due to a resonance phenomenon called the Kármán vortex street, a phenomenon arising in fluiddynamics with a certain resonance frequency, called the Strouhal frequency. ...

5

What you are seeing on the square plate are the resonant modes of the structure. Each of these modes has a particular frequency associated with it, and is rung up when the plate is driven at that frequency. These resonant modes act like standing waves on a string: where some parts of the plate are moving a lot while other parts are standing still. The sand ...

5

Put more simply: sound waves are attenuated as they propagate through air (this is more easily measured for very short wavelengths, e.g. ultrasound). This means they lose energy - which is turned into heat of the air. The amount of heating, however, is very very small. Let's do the math. A sound wave of 120 dB (really loud) has energy of only $1 ... 5 Normally, suspension consists of a damping component and a spring component. For such a suspension, higher speed means higher acceleration and greater force. Driving faster will cause a bigger jolt. However, high end cars these days use active suspension - and that changes everything. With active suspension, you can either respond quickly to bumps in the ... 4 The trouble is that your table, or whatever object it is, will act as a waveguide. That's because the sound waves will (partially) reflect of the wood/air surface then travel back into the table and interfere with other waves. The result is going to be hideously complicated to calculate. As Luboš says in a comment, if the thickness of the table is much less ... 4 Taste and smell are mediated by receptors in your body that molecules can attach to. These receptors then give off an electrical signal which is translated in the brain to a certain taste or smell. The details of this are biological and not of importance here. So no, there is no relevant frequency or even wave-like behavior. Touch is a very different thing. ... 4 I don't mean to take anything away from the previous great answers, but the "simple and to the point" answer is, a very qualified, yes. By qualified, I mean one must know the coin's composition, thickness, diameter(or shape), density distribution, country of manufacture, etc. If we make assumptions and restrictions, then it becomes possible to calculate ... 3 Taste: There are 5 basic tastes that the human tongue can detect. They are sweet, savory, salty, sour and bitter. These are detected by taste receptor cells on our tongue, I won't go deep into the biology part. The basic tastes of sweet, salty and sour have different thresholds, or concentration levels, at which they can be detected. In other words, it is ... 3 Not a complete answer, but this is a classic "sloshing" problem. The interaction between the fluid and the container wall, under the influence of the external (periodic) force sets up a (self-reinforcing) and harmful resonance. This is of immense practical interest: jet-fuel sloshing inside airplane tanks, for instance. 3 When you pluck a string it does not start out like the fundamental above. The string is pulled into a bent shape of two straight lines and an angle and it may not be bent at the middle. Releasing the bent string causes a bunch of harmonics of various amplitudes depending on how far off-center it was bent. (It can not return to the bent angle shape and the ... 3 If the bell is still vibrating when you let air inside it, then the answer is yes. If the bell was damped just before the door is opened, then the answer is no. Sound is transmitted through compression / decompression waves (pressure waves) in a medium (e.g. air, water, wall). This necessitates contact of the vibrating source of sound with such a medium. ... 3 A plank is a complicated example to choose because it's a composite material with a complicated structure. A better choice would be a piece of iron or some other homogeneous material. In that case the speed of sound is given by: $$v = \sqrt{\frac{K + \tfrac{4}{3}G}{\rho}}$$ where$K$is the bulk modulus and$G$is the shear modulus. The bulk modulus is ... 3 Heat corresponds to random movements of atoms and molecules. It travels only through conduction - slowly. Sound consists of ordered movements, travelling through a medium as a wave (although it can also stand still, as in a standing wave). Large numbers of atoms or molecules move back and forth in synchrony. Sound eventually becomes random, as it is ... 3 Regardless of whether the "local" situation is symmetric or not with respect to loosening and tightening, what you essentially have is a random walk. At any point in time, the screw can stay where it is, get a little looser or get a little tighter. There is, in practical terms, a limit as to how tight the screw can get but no limit on how loose. For any ... 3 No, because in a vacuum, there is no way for the two tuning forks (I think you meant this, rather than pendulums) to communicate. The reason a second tuning fork with the same resonance frequency will begin resonating is because, physically, sound waves are hitting it at its natural frequency. Sound waves travel in a medium, so in a vacuum, there's nothing ... 3 The amount of energy lost to vibration in a car engine is typically very small. You can see this easily because the vibration (and the energy associated with it) is dissipated in the engine mounts, and if any significant amount of energy were being dissipated the engine mounts would get hot, which they don't. Most of the inefficiency is because the ... 3$y(\theta) = A\sin \theta+ B \cos \theta\$ is known as the simple harmonic function. All the motions which can be represented by this function are known as simple harmonic motions. Motion of a simple pendulum is approximately a simple harmonic motion for small amplitudes. It stops vibrating after some-time due to drag from air i.e. loss of energy. But, we ...

2

It looks like you're asking for some historical view of how the idea of vibrating air was formed. I honestly don't know, but I can tell that the idea of things acting at a distance has been rejected through history (even Newton thought that his gravitation theory had a flaw at supposing the force acted at a distance, potentials partially solved that), so I ...

2

String theory, a-la Briane Greene's "The Elegant Universe" (which bears very little resemblence to actual string theory).

2

In principle, there is now reason that this can't be done. There are, however, a lot of practical difficulties. You would need a high speed camera recording at something like 50,000 fps to catch all of the audio band which humans can hear. These things aren't cheap and generally can't record for longer than a few tens of seconds at such high speeds. ...

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