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72
votes
6answers
5k views

Why do tuning forks have two prongs?

I believe the purpose of a tuning fork is to produce a single pure frequency of vibration. How do two coupled vibrating prongs isolate a single frequency? Is it possible to produce the same effect ...
41
votes
1answer
1k views

Why does our voice sound different on inhaling helium?

This question (and answer) is an attempt to clear the air on what appears to be a very simple issue, with conflicting or unclear explanations on the internet. Arguments, negations, etc are invited. ...
16
votes
1answer
902 views

Why don't tuning forks have three prongs?

I was reading Why tuning forks have two prongs?. The top answer said the reason was to reduce oscillation through the hand holding the other prong. So if having 2 prongs will reduce oscillation loss, ...
13
votes
2answers
556 views

Is the length of the day increasing?

In Frontiers of Astronomy, Fred Hoyle advanced an idea from E.E.R.Holmberg that although the Earth's day was originally much shorter than it is now, and has lengthened owing to tidal friction, that ...
10
votes
3answers
533 views

Resonances in high energy physics

I still do not understand what a resonance precisely is. Is it exactly the same as a particle? Or only an excited state? And why does it make a peak in some diagrams? And which diagrams?
9
votes
1answer
400 views

Why do you only hear high frequencies when a microphone is near its speaker?

The phenomenon I'm talking about is positive feedback, as known from control engineering: when the microphone is too close to its speaker, it can "hear itself", so the signal will be infinitely ...
8
votes
1answer
549 views

Theory behind patterns formed on Chladni plates?

In this video of vibrating Chladni plates we can see small sand particles align themselves into different interesting patterns (also shown in the image below) which correspond to some particular ...
7
votes
3answers
4k views

Does the human body have a resonant fequency? If so, how strong is it?

Inpired by http://music.stackexchange.com/questions/7064/physiological-responses-to-different-rhythms, I'm wondering if the human body has a strong resonant frequency. I guess the fact that that it's ...
6
votes
1answer
238 views

Why do we hear this mysterious sound?

Sit in a silent place and then bring your hands close to your ears and cover your ears, you will start hearing some sound but if you remove your hands you don't hear it anymore. Can anyone explain ...
6
votes
2answers
977 views

Lots of little questions about radiation of LC circuits

I'm trying to get a more intuitive understanding of resonant inductive coupling. It's supposed be a more efficient way to transfer electrical energy wirelessly, because the coils are only coupled by ...
5
votes
2answers
195 views

How can I use sound/resonance to clean sewers?

This probably doesn't fit into the realm of regular questions ; it is more of an applied rather than theory/math question ... Anyway, I'm curious whether a metre diameter speaker fitted over a ...
5
votes
0answers
75 views

To what degree does guitar construction affects the vibration of the strings?

There's an old debate going on in the guitar community about how much does wood choice and body shape affect the sound of an electric guitar. No one denies that there's a difference acoustically (how ...
4
votes
1answer
209 views

Why does a container with fluid make different sounds at different fluid levels?

Have you ever noticed that when you are filling a container with fluid. As it approaches the top, it makes a different sound? You can tell by listening when your about to reach the top. Why is this?
4
votes
1answer
59 views

Is this oscillator driven?

A mass $m$ is attached to a vertical massless spring or a spring constant $k$. Originally, the spring was relaxed because the mass was held by a clip. Suddenly the clip was released. THe mass ...
4
votes
4answers
2k views

How does radio receives signal from particular station?

When you tune your radio (digital or analog) to receive say 100 MHz frequency and while in the environment there are hundreds of channels everywhere around the radio. How does it chooses to receive ...
3
votes
3answers
2k views

Why do we take the first derivative of EPR/ESR spectra?

Apologies if this question is a bit too chemistry-flavoured. In electron paramagnetic resonance spectroscopy, there's a practically ubiquitous convention of plotting the first derivative of the ...
3
votes
1answer
206 views

Free/open source tools for calculating normal modes, failing that, advice

Are there any open source tools for calculating the normal modes of arbitrary objects? Input would be some 3D design format and material properties, output would be movement direction and magnitude ...
3
votes
1answer
182 views

Can soldiers marching at the right frequency realistically cause a bridge to break?

In my physics class it was suggested that ancient armies had a rough understanding of the idea of a resonant frequency and so they "broke step" when crossing bridges so as to avoid a very high $Q$. I ...
3
votes
2answers
313 views

How might a resonant antenna and black body radiation interact?

How does an antenna behave when it is cooled so that its black-body radiation is emitting energy at its resonant frequency? Edit: To clarify, its not how they're related in general, but how might ...
3
votes
2answers
54 views

Why does a wine glass with less water resonate at a higher frequency?

In this video https://www.youtube.com/watch?v=hWwM7F-zaHs, Professor Lewin showed that for the tube, the less water there is, the longer the effective length of the tube and therefore, the lower the ...
3
votes
1answer
836 views

Static flow of water in the presence of a loudspeaker

The title, I don't know whether it's correct or not, but I came across a video in youtube, http://www.youtube.com/watch?v=_PkgQQqpH2M. The author of video used the title and hence I used the same. ...
3
votes
1answer
1k views

Is it possible to break bulletproof glass with your voice?

In The Adventures of Tintin, an opera singer (the Milanese Nightingale) broke a bulletproof glass case using her voice. Is that scientifically possible? From the Wikipedia page, a typical bulletproof ...
3
votes
1answer
115 views

Is using a swing an example of normal or of parametric resonance?

Parametric resonance is a situation where the driving frequency is a multiple of the eigenfrequency. Various people say that using a swing and propelling it oneself is such a case, with the driving ...
3
votes
1answer
99 views

Electron Spin Resonance and Free electrons

When performing an experiment to observe electron spin resonance, we use DPPH molecules as they contain an unpaired electron on one of the N atoms. My question is, why cant free electrons be used in ...
3
votes
1answer
992 views

How does a stronger magnet affect the MRI image quality?

In which ways is a stronger magnet better for magnetic resonance imaging? I read that: The field strength of the magnet will influence the quality of the MR image regarding chemical shift ...
3
votes
1answer
67 views

Can a room resonate at a frequency lower than the principal frequency?

I'm the bass in our high school a cappella group. Recently we had a performance in our auditorium, and I am almost certain I heard the pitch an octave lower than I was singing. I was singing E3 (164 ...
3
votes
0answers
176 views

Calculation of a Gravity Resonance Keyhole

Can anyone describe the mathematics behind the calculation of a resonance keyhole (for a two-body model)? It seems like the size and position of the keyhole should be a function only of mass and ...
2
votes
2answers
3k views

Phase difference of driving frequency and oscillating frequency

If a mass is attached to a spring and is oscillating (SHM). If a driving force is applied it must be at the same frequency as the mass's oscillation frequency. However I'm told that the phase ...
2
votes
3answers
102 views

Are there any musical instruments which use resonance tubes with two closed ends?

Many musical instruments use resonance tubes with one closed end - all brass instruments (I think), clarinet, etc. There are also instruments where both ends are open (flute, pipes) Are there any ...
2
votes
1answer
676 views

Can sound be used to purify/filter water?

I remember reading about all chicken at a poultry farm being violently sick/dying for apparently no reason. It turned out the culprit was machinery at a nearby factory that emitted sound at a ...
2
votes
2answers
138 views

How does energy transfer between B and E in an EM standing wave?

I'm trying to understand how an electric field induces a magnetic field and vice versa, its associated energy, as well as relating it to my understanding of waves on a string. Using a standing wave ...
2
votes
1answer
667 views

What is the difference between Feshbach resonance and Fano resonance?

What is the interpretation of "resonance" in Feshbach resonance and Fano resonance? What is the difference of Feshbach resonance and Fano resonance?
2
votes
1answer
295 views

Singing: Resonance body open-closed or closed-closed?

Googling yields contradictory results, so here my question: When I sing, my vocal chords vibrate, but my whole body is the resonance body, right? So I would say that when I think about standing waves ...
2
votes
1answer
46 views

Decuplet baryon resonances

Are all baryons from decuplet resonances?? Because all resonances decay by strong interaction; but omega minus baryon can't decay via strong, because any other bound state with strangeness -3 exists. ...
2
votes
1answer
51 views

What does it mean for an electromagnetic structure to be resonant?

There are many electromagnetic structures used in microwave engineering and EM devices. For example, patch antennas, metamaterials made from unit cells, etc. When they design structures like patch ...
2
votes
1answer
57 views

Tuned Mass Damper

I was learning about the different applications of resonance and one of them is the tuned mass damper used in buildings. One thing I am confused about is as to why the mass attached to the building ...
2
votes
1answer
740 views

Harmonics in an open organ pipe

How to solve the following question? An open organ pipe has two adjacent natural frequencies of 500 and 600 Hz. Assume the speed of sound in the air 340m/s. The length of the organ pipe is? What ...
2
votes
3answers
2k views

Frequency of a Tuning Fork

Question: Which of the following affect the frequency of a tuning fork? Tine stiffness Tine length The force with which it's struck Density of the surrounding air Temperature of the surrounding air ...
2
votes
2answers
116 views

Harmonic Oscillator driven by a Dirac delta-like force

Consider that there is no damping for simplicity. As we know, a driving force of the form $\sin(\omega t)$ will make the oscillator at steady state vibrates at the external frequency $\omega$. What ...
2
votes
1answer
254 views

Why does the addition of paramagnetic ions decrease the spin lattice relaxation time of protons?

My question pertains to NMR (nuclear magnetic resonance). $T_1$, the spin lattice relaxation time of protons in water is about 2.5 seconds. If you add some $CuSO_4$ (copper sulfate) to the water the ...
2
votes
1answer
1k views

Does the Breit Wigner formula apply to intermediate virtual particles?

Breit Wigner Formula describes the cross section for interactions that proceed dominantly via a intermediate particle (O*) A+B → O* → C + D: $$σ = \frac{2\Pi}{k^{2}}\frac{Γ_{i}Γ_{f}}{(E-E_{o})^{2} + ...
2
votes
2answers
194 views

Drum head coupled with an RLC circuit

I'm thinking about the possibility of an electroacoustic drum that would be tuned with some kind of RLC circuit. The drum head would have an electromagnet attached to its center, which would be ...
2
votes
1answer
292 views

Complex valued energy

I'm working on a 2D He superfluid system with vortices. I was asked to calculate the kinetic energy of vortex-(anti-)vortex pairs and compare the two situations. One finds in literature that the ...
2
votes
3answers
945 views

How could this person have discovered the resonant frequency from this string of magnets?

I stumbled onto this page http://mylifeisaverage.com/story/1364811/ and the post states that they were all making strings and shapes with these sets of 216 really small spherical earth ...
2
votes
1answer
46 views

Standing sound wave in a wind instrument

So I've had this question bugging me ever since I saw sound at physics class: How is it possible to match the resonance frequency of a column of air in an organ pipe and form a standing sound wave by ...
2
votes
1answer
66 views

What is sympathetic resonance?

When two tuning forks stand near one another and one is excited, the other rings as well. When high notes are struck on a piano, lower notes are also heard. If I understand correctly, this is called ...
2
votes
0answers
35 views

Resonance condition in confocal cavity

In a confocal cavity, a beam traverses the length of the resonator 4 times between two transmissions along the same ray. . For example, in the above figure, path difference between two beams that ...
2
votes
0answers
33 views

Math formula for crystal glass resonance [duplicate]

For a music therapy experiment, I have to use several crystal glasses with water and different cylindrical shapes, and make them vibrate and produce different sounds. Is there a math formula that ...
2
votes
0answers
54 views

Reflector Klystron and Isolator for ESR/EPR Experiment

I am doing a lab on ESR/EPR, and I would like to know how the reflector klystron operates. It is very old and the company who made our model does not exist anymore and there are no operation manuals. ...
2
votes
0answers
350 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 ...