# Tag Info

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 ...
• 33.9k

Since the phases are random, the waves do not add coherently... but neither do they cancel coherently. Furthermore, loudness is really a measure of the intensity of the sound. Thus, if we consider a ...
• 39k

### 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 (...

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

I don't think this question as posed is really well defined. But here's an attempt at an answer. In the real world the answer is yes. Assuming the train is longer in the direction of motion (as is the ...
• 34.3k
Accepted

### Confusion with Doppler effect problem

Consider, by analogy, a small, fast boat sitting almost motionless in the open ocean. It's moving just fast enough to maintain steerage way, and keeps moving slowly with a following sea. The waves ...
• 10.2k

### Confusion with Doppler effect problem

insipidintegrator wrote: "But when the speed of the detector exceeds that of sound, the sound waves which are subsequently emitted by the source will never be able to reach the detector. " ...
• 7,757

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

Yes, because the train predictably hits bumps/gaps in the track. As you travel on a train, you hear first one set of wheels then the other then the other going from the front of the train to the back ...
• 1,019

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

The simple answer is no, you would not be able to know. In fact you would not even be able to know that you are traveling at a constant speed. To you, the train could be completely still (assuming ...
• 848

### Confusion with Doppler effect problem

There are four distinct phases for the situation in question: Subsonic movement As the detector moves ever faster away from the source, the frequency of the waves drops because the waves move slower ...

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

I never seen a train overtaken by another train in a parallel adjunct track lane. Usually there are trains bypassing opposite direction to each other from parallel track lanes. I think it would be ...
• 3,186
Accepted

### How to derive the energy density of a sound wave?

Notes: I believe that the answer you are trying to obtain is incorrect. First, if you are looking at total energy density, you should not have the factor of 1/2. Alternatively, you could be looking ...
• 1,392
Accepted

### Is there an electromagnetic analogue of thermoacoustics?

Yes, you are describing a waveguide which is a pipe that is used to conduct microwaves. It is possible to build standing electromagnetic waves inside such a pipe, giving rise to the klystron and ...
• 73.8k

### Why can thin sponge lining soundproof earmuffs but not walls?

It's because the effectiveness of different noise-abatement treatments depends on the frequencies that the noise source contains, and whether the objective of the treatment is to absorb reflected ...
• 73.8k
Accepted

1 vote

### Bottle Marimba calculations?

Most important: First, I would suggest, WEAR SAFETY GLASSES. If a small piece of plastic embeds itself anywhere in your body, the damage will almost always be reparable, unless it's in your eye. It ...
• 2,832
1 vote

### Help me find a material with low acoustic impedance but high wave velocity

It looks like you want to maximize the ratio between wave velocity and acoustic impedance. Let say we call it "p". But this is just the inverse of density. The stiffness is irrelevant. ...
• 6,568
1 vote

### Help me find a material with low acoustic impedance but high wave velocity

Low acoustic impedance comes from a low product of density and stiffness. High wave velocity comes from a high ratio of stiffness to density. So, your requirements favor low density but conflict on ...
• 4,103
1 vote

### Does a tower bell ringing prevent thunderstorms?

The energy scale of thunderstorm is much larger than that of a bell (most other devices built by humans), so it is unlikely that such devices can affect thunderstorms in a controllable way. A single ...
• 1,778
1 vote

### Why are traditional telephone lines limited to about 3-4 kHz bandwidth?

Telephone company operators used to physically patch one wire to another to make a dedicated line from end user to end user. Certainly parasitic capacitance had a limiting effect. But today, ...

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