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 ...
- 10.4k
51
votes
Accepted
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 ...
- 13k
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 ...
- 663
35
votes
Accepted
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 ...
- 89.3k
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 ...
- 3,780
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, ...
- 97.8k
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 ...
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 ...
- 97.8k
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 ...
- 105k
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 (...
- 35.5k
15
votes
Accepted
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) = \...
- 363k
14
votes
Accepted
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 ...
- 12.7k
14
votes
Accepted
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 ...
- 3,116
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 ...
- 61.8k
14
votes
Accepted
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 ...
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 ...
- 17.1k
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 ...
- 141
14
votes
Accepted
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 ...
- 60.3k
13
votes
Accepted
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 ...
- 12.9k
12
votes
Accepted
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{...
- 30.2k
11
votes
Accepted
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 ...
- 15.5k
11
votes
Accepted
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 ...
- 801
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 ...
- 490
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 ...
- 1,297
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 (...
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 ...
- 928
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 = ...
- 915
9
votes
If all harmonics are generated by plucking, how does a guitar string produce a pure frequency sound?
For an ideal string, the key point is that all the harmonics are "harmonic" : their frequency is a integer multiple of the frequency of the fundamental. So the movement of the string is periodic and ...
- 4,936
9
votes
Can mass be ejected from a black hole within the Schwarzschild radius?
This exceprt doesn't quite get what a black hole is. Once you're inside the Schwarzschild radius, it's not that "you can't go fast enough too get out", it's that the idea of "going outside of the ...
- 41.9k
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