93 votes

Intuitively, what actually is the cause of resonance?

For intuition I find it easier to start with a regular pendulum. Imagine a steel ball on a string hanging down. If you give it a push, it will start to swing back and forth. Now if you, while the ...
noah's user avatar
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50 votes
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Why do string instruments need hollow bodies?

Yes, the room has a lot of air, but most of it isn't in direct contact with the vibrating string. In order for the string to make much sound, it needs to transfer some of its energy to the surrounding ...
PM 2Ring's user avatar
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42 votes

If sound passes through material, vibration is produced. So are electromagnetic waves produced too?

A sound wave passing through a medium (e.g. air) indeed displaces molecules by a distance of a few nanometers. It seems reasonable that it should also displace the atoms, and thus electrons and ...
Cyclone's user avatar
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35 votes
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Can the vibrations from the Earth affect gravitational wave detectors?

Summary Yes they can. False positives arising from the acoustic sources you name are ruled out by seismological analysis and the examination of correlation between the separate gravitational wave ...
Selene Routley's user avatar
30 votes

Intuitively, what actually is the cause of resonance?

If you have ever learned how to swing on a swing set then you have directly applied resonant forcing. By moving your body in the right way in time with the swinging motion, you can add more energy to ...
Kai's user avatar
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24 votes

What causes this strange noise in a pair of walkie-talkies?

It's called feedback . Here is what happens: When Alice presses TRANSMIT, it turns on the microphone in her radio and hence begins to transmit any noise that hits the mic. With Bob's radio on RECEIVE, ...
niels nielsen's user avatar
21 votes

If all harmonics are generated by plucking, how does a guitar string produce a pure frequency sound?

Usually, a guitar does not produce a pure tone/frequency. If so, its sound would be very close to a diapason. The difference between noise and a musical tone is not that a unique frequency makes a ...
GiorgioP-DoomsdayClockIsAt-90's user avatar
19 votes

Magnetic field changes induced by vibrating electric guitar string

Here's what's happening: The permanent magnet in the pickup propagates a static magnetic field which extends out from the magnet tip. The ferromagnetic string resides within this field. Because the ...
niels nielsen's user avatar
18 votes

Non-resonant but efficient frequencies

This is a subtle issue! Your intuition is correct (a driving at $f_0/2$ should be very effective) even though the graph seems to contradict this. The reason is that the graph displays the response to ...
knzhou's user avatar
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16 votes

Why does a metal block make a shrill sound but not a wooden block upon hammering?

Is it that the wooden block vibrates with lesser frequency than the metal block? If so, why is that? 'Yes', to the first question. Metal is stiffer than wood and produces higher frequencies (...
Gert's user avatar
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15 votes
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If all harmonics are generated by plucking, how does a guitar string produce a pure frequency sound?

Human perception is involved here because when you humans talk about noise this generally means a sound that is aperiodic. However the tone produced by a guitar will be something like: $$ A(t,x) = \...
John Rennie's user avatar
14 votes
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Does plucking a guitar string create a standing wave?

Yes, plucking a guitar string does create standing waves, but... No, plucking a guitar string does not create a standing wave, as the sum of standing waves is in general not a standing wave (thanks ...
stafusa's user avatar
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14 votes
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Why does a metal block make a shrill sound but not a wooden block upon hammering?

The metal block has a relatively low level of internal damping, however the wooden block has a high level of internal damping: Much of the energy imparted to the wooden block is dissipated internally ...
user45664's user avatar
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14 votes

Vibration in a guitar when playing two strings

The first image shows a string oscillating at its fundamental frequency $f$. The second image shows a string oscillating at $2f$. The third image shows a string (or the wooden soundbox of a guitar ...
Andrew Steane's user avatar
14 votes
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If sound passes through material, vibration is produced. So are electromagnetic waves produced too?

If it passes through a piezoelectric material, it may generate a measurable voltage and current, some fraction of which will be radiated. For most materials, however, there won't be a detectable ...
Cristobol Polychronopolis's user avatar
14 votes

Why does glass, in spite of being amorphous, often break along very smooth surfaces?

What you describe is the cleavage type of fracture of polycrystalline material. The surfaces are smooth, but the micro anisotropy due to the several grains can be seen in a scanning electron ...
Claudio Saspinski's user avatar
14 votes

Why do string instruments need hollow bodies?

The soundboard is the crucial component in acoustical amplification of string vibrations. The strings pass over the bridge, which is solidly attached to some part of the soundboard. A vibration at the ...
Glyn Adgie's user avatar
14 votes
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Playing cymbals in vacuum

When you strike cymbals (or any other object) you give them a certain amount of energy. If the object is stiff and light (like cymbals) this energy will cause the object to vibrate. The vibrations ...
gandalf61's user avatar
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13 votes
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How does a guitar work?

The string oscillations are mainly transverse (a standing wave). The string motion causes the tension to oscillate thus applying a varying force on the guitar top through the bridge and saddle. The ...
safesphere's user avatar
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12 votes
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Energy of molecular vibrations

It does depend on the mass, but mass it is not explicit in the equation $$E_n=(n+\frac12)\hbar\omega$$ but it is implicit. In the equation above we have the vibrational frequency $$\omega=\sqrt{\frac{...
joseph h's user avatar
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11 votes
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Why don't metals damp vibrations?

Damping implies a loss mechanism. In liquids, where molecules move freely in close proximity, this loss mechanism is a transfer of momentum from one molecule to another. In pure crystalline metals, ...
Floris's user avatar
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11 votes
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Forced Oscillation Explained with Violin String

In musical instruments, none of the excitations, whether by bowing, plucking, reed vibration, lip vibration, striking, etc, are sinusoidal methods. Therefore, they all, by Fourier's theorem are ...
Bill N's user avatar
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11 votes
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Why does plucking a string produce harmonics instead of a pulse?

It does produce a pulse. However, the speed of sound in a string is very large so the pulse reaches the ends of the string very quickly. This means that in a second many reflections occur and you only ...
Miguel Correia's user avatar
11 votes

Magnetic field changes induced by vibrating electric guitar string

Although niels nielsen's answer contains valuable information (the last 3 paragraphs), I think user1079505's answer is closer to the truth, and the article (that I don't have access to) hinted at by ...
Zaaikort's user avatar
  • 492
10 votes

Non-resonant but efficient frequencies

First I'll try to explain why the amplitude vs frequency diagram only has one maximum, then I'll go back to why this seems to contradict your intuition. Let's take the simplest forced oscillator ...
Lucas Gautheron's user avatar
10 votes

Eyes shut, can a passenger tell if they’re facing the front or rear of the train?

I think you might be able to distinguish the direction of motion by turning sideways and listening for the apparent motion of the clickety-clack sounds and vibrations from the carriage wheels (...
Spehro Pefhany's user avatar
10 votes

Magnetic field changes induced by vibrating electric guitar string

Electric guitar strings are ferromagnetic. In the presence of magnetic field from the magnets in the pickup, the strings become magnetized. As they move (vibrate), the magnetic field they generate ...
user1079505's user avatar
9 votes

Why do tall buildings have low resonant frequencies?

We can model a short building as a uniform cuboid of density $\rho$ occupying the region $$0 \le x \le L_x$$ $$0 \le y \le L_y$$ $$0 \le z \le L_z$$ with its mass given by $$M = \rho V = \rho A L_z = ...
Bio's user avatar
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9 votes

Why don't metals damp vibrations?

I'd like to point out the example of cast iron. It is renowned for its excellent vibration-damping properties. It is wrong to reach a blanket conclusion saying that metals are bad for vibration ...
don_Gunner94's user avatar

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