Tag Info

2

Sound waves can be emitted not only by vibrating bodies, but whenever there are pressure differences as the result of thermodynamical instability. Therefore even putting out the cigarette can produce sound cause of high temperature (and therefore pressure) differences. It's not an event with pronounced frequency characteristics, because the differences ...

0

One example. One item. A very well-known in the physical world. The so-called Doppler effect. This has taken all together more than 35 years before recognizing was a fact. BibTex @article{tuinstra2009lotgevallen, title={De lotgevallen van het dopplereffect}, author={Tuinstra, Fokke}, journal={Nederlands Tijdschrift voor Natuurkunde}, volume={75}, ...

1

You correctly assumed that sound in space does not propagate ( the density of gas molecules is between 1 per cubic meter and 1 per cubic centimeter, too low to efficiently propagate sounds ). But the Camera is mechanically attached to the space suit, which contains various mechanical parts, like a thermal control system to manage the temperature inside the ...

0

Well, if I'm not mistaken, it's pretty straightforward. Let $p(r, \theta, t)$ be separated in two functions with variables of time $T$ and spatial variables $\Theta$ (I'm not using $R$, cause it's already defined): $$p(r,\theta,t)=\Theta(r,\theta)T(t)$$ then: $$T = e^{i\omega t}$$ $$\Theta = i\frac{Q\rho c k}{4\pi R}e^{-ikr}$$ $T$ is given ...

1

Perhaps I could share some idea for further research. If we could make actual and correct pressure measurements in the cochlea to reveal wether the non-stationary Bernoulli effect is a good description of the actual physics-of-how-the-cochlea-isolates-frequencies-along-its-length? I would consider: I would propose to use a pitot tube, with sensor in the ...

4

The cochlea has a complex physical structure, with multiple membranes and fluid-filled chambers. Therefore to explain the separation of frequencies along the basilar membrane of the cochlea is complex to. Sure, there are a lot of very general descriptions (even the answer of theblackcat) and a lot never go into the actual physics of the system. This ...

1

The reason D is the "correct" answer, is because the key word best, is used. Although any answer may not be 100% correct, if at least one of the answers is better than the others, then that would make it the correct answer. A and B are eliminated because the amplitude should decrease as one moves away from the XY center line. C is eliminated because it ...

1

Here's an article about acoustic version of laser named SASER. http://en.wikipedia.org/wiki/Sound_amplification_by_stimulated_emission_of_radiation It can emit very directed acoustic field. As far as I know, present versions have quite limited posibilities, but if you're writing SF it may be inspirational.If SASER's wave can propagate in human body, which ...

0

I tend to disagree. Acoustic levitation is based on the standing waves phenomenon and therefore it needs a bit time to be established. Emmiting a ray of sound to hit the bullet is not a good way to deviate it from its path. If I was a sci-fi engineer in the field of acoustic defense, I would create walls of standing waves with knots and antiknots organised ...

0

So far the best commercial unit I've found for this is this one: http://www.enoscientific.com/well-watch-600.htm They use a 60 hz audio signal, with some signal processing to reject false returns and do edge detection. It records to a flash card, has a USB port for downloading, and optional radio access.

1

One of the ways of motivating the multipole expansion is as follows: consider a system of charges (more generally, sources, but let's consider the electrostatic case in particular) $q_i$ with position vectors $\mathbf{r}_i$. We want to calculate the electrostatic potential (more generally, whatever field you are interested in) $\phi$ at a point $\mathbf{R}$, ...

0

1

1/f spectra have the unique distinction of being "scale invariant" in the sense that the energy in an interval df is proportional to df. The 1/f spectra in fact have the property that the in an interval with width df available energy is proportional to df but not with f. There, namely "scale invariant" attribute for. It is not the energy, but the signal ...

1

From the Wikipedia article on fog: Sound typically travels fastest and farthest through solids, then liquids, then gases such as our atmosphere. The distance the water molecules are from each other, and temperature, are the reasons sound is affected during a fog condition. Molecule effect: Though fog is essentially water, the molecules are barely ...

14

According to this link sound (especially high frequency sound) is more attenuated in fog, because it is dispersed by the (billions of) air-water interfaces of all the droplets. This is one reason why a fog horn is a very low sound - low frequencies travel further, especially in fog. For echolocation you want to use high frequencies, and fog is more ...

0

I am not sure if you mean something like this, since it is man-made but it does not include engines: The tip of a whip can move faster than the speed of sound, this is why it creates this loud noise. see http://en.wikipedia.org/wiki/Whip for some further information.

0

Tsunami waves are very fast. Speed of tsunami wave in deep ocean may get higher than the speed of sound in the air: http://wcatwc.arh.noaa.gov/?page=tsunami_science

1

Neutrinos passing through you. Photons from the sun. The tangential velocity of many points on the Earth. The speed of beta particles.

1

For our three compartment hearing sense, from a physics point of view, there is a basilar membrane stimulation, from base to apex, in its pathway in the cochlea, to a place on the basilar membrane. By periodic movement of perilymph, non viscous fluid, backwards and forewards, in the cochlear duct meet the conditions of a potential flow. The basilar ...

0

However interesting, your question is probably too broad. When it comes to perception (so not just simple objective values), this topic is actually not perfectly understood in general. Always remember, that perception of any parameter of the sound is nonlinear and dependent on other parameters (e.g. you need to consider a pitch of the tone, when you ...

0

If it's suspended by a magnetic field, then ringing will cause a disturbance of the field. This will cause radiation of electro-magenetic energy. The same is also true of the gravitational force the bell exerts on it's self. The ringing will cause gravitational radiation (loss) of energy. Assuming that the bell is the size and density of a large black ...

4

Anything that "suspends" the bell - whether it be a bolt, a piece of string, or a magnetic field - is applying a force. When the bell vibrates, this vibration will be transmitted. This is because the force of a magnet is a function of position - you can only get magnetic attraction because of a divergence of the field, so if you move, the force changes and ...

0

Yes, it will end. When the bell rings, one side gets closer to the one magnet then the other. The other side gets further away from a magnet. This makes the force in one direction pull on the side as it goes back, eventually stopping the magnet. If we ignore this, then the bell will still stop, considering the force of gravity and how it stops all simple ...

5

Internal friction in the metal of the bell eventually will bring the ringing vibrations to an end. The bell vibrates when it rings, making its molecules more energetic and creating heat. Bonding between the molecules of the bell resist the vibrations, and eventually the strength of the molecular bonds will create enough friction to bring the vibrations ...

1

I know this question is technically already answered, but there were several things missing from the answers that I thought should be mentioned (I am writing a review paper comparing different regions of space so I had these numbers at hand already as well). The speed of sound in space has multiple meanings because space is not a vacuum (though the number ...

2

The round trip time of the ping is unknown; but we do know that the difference in round trip time between sub stationary and sub moving is 0.02 seconds. Let us write $D$ for the distance to the cliff when you send the ping; if you are traveling at a speed $v$, and the speed of sound in water is $c$, then we can write down the round trip time as follows ...

2

Your error is that you assume it takes 2.00s seconds for the ping to reach the cliff and an additional 1.98s to return. Without knowing the distance to the cliff, we can't qualify that assumption. Besides that, the only thing we need for the calculation is the difference in period of the outgoing and incoming pings. With a single ping you can calculate the ...

4

I find the explanation given in the first paragraph of Wikipedia article is pretty good. Let me just elaborate some aspects to make it more clear. Megaphone is simply an extension of your vocal tract. Therefore the acoustic impedance of the whole system rises so the pressure and volume flow variations at your vocal chords may grove. A trade-off is ...

3

When one shouts , the sound waves disperse in a semicircle , the power of the voice cords distributed to 180 degrees. A simple megaphone channels the sound in a small angle and thus is directional and stronger. Electric megaphones amplify the sound and still send it in a narrow cone. At the output of the cone the sound wave spreads, but it still is much ...

2

The speed of sound is given by: $$v = \sqrt{\gamma\frac{P}{\rho}} \tag{1}$$ where $P$ is the pressure and $\rho$ is the density of the gas. $\gamma$ is a constant called the adiabatic index. The equation should make intuitive sense. The density is a measure of how heavy the gas is, and heavy things oscillate slower. The pressure is a measure of how stiff ...

0

Sound waves propagate through a medium as the result of collisions between molecules. At higher temperatures, molecules have greater kinetic energy, and as they move faster their collisions occur at greater frequency and they carry sound waves faster. Greater kinetic energy = less inertia = increased speed. However, as sound waves are compressional waves ...

2

Yes sound is a goldstone mode. Consider, for example, an ideal gas with particles at positions $\mathbf{x}_i$. There is a symmetry where we can displace each particle by some displacement $\mathbf{u}$. Of course this symmetry breaks spontaneously. By definition, we only observe $\mathbf{u}=\mathbf{0}$. The goldstone modes corresponding to this symmetry are ...

0

Yes, it's like that. You have described the basic conception of retarded potential in acoustic radiation (which will be one of the typical relativistic topics in electromagnetism). You have not specified the medium between the device and the listener but it actually doesn't matter. For more media you only need to specify more times and subtract them all ...

Top 50 recent answers are included