# Tag Info

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Acid Jazz is quite right. Generally any instability in air medium can result in sound waves radiation. Vortices causes local pressure instabilities and the medium is "able to propagate the image of it" (well, the Wave equation). Kármán vortex street is nice (and most of all solvable!) example of vortex shedding. But in certain domain of the Reynolds number ...

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The frequency of a signal is hard to change. Some ways that you can change it: reflect it off a moving object change the distance between source and receiver as a function of time (Doppler shift) introduce some non-linear amplification - this will generate harmonics If you just add "noise" (uncorrelated to the signal), you can create constructive or ...

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The underlying principle is to use interferometry and the Doppler effect to remotely measure the velocity of a reflecting surface. When a moving object is illuminated with coherent light it reflects it with a wavelength shift proportional to its velocity. This is the well-known Doppler effect. The frequency shift relates to the source's velocity as ...

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If the space is truly "open", then reflection should not play (since there is nothing to reflect off), and refraction can only play if there is a change in refractive index (which "normal air" would not have). That seems to leave two things: the fact that the entire body vibrates when you speak - and thus there is some fraction of the sound being directed ...

1

Generally that would be diffraction - the spreading out of a wave. Reflection is bouncing off objects - e.g. an echo of someone's voice. Refraction is about a wave changing direction e.g. water looks shallower than it is when viewed from above in air because the light from the bottom is refracted (bent) at the water/air surface. In this case - diffraction - ...

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Best hypothesis so far is that as gas density increases the transducer couples more efficiently to the medium, giving the impression of a decrease in absorption coefficient due to the increased amplitude at the receiver.

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Typically not. Changing the frequency requires some non-linear process and background noise is simply additive. There potential exceptions: the noise could be so loud that the air and/or the microphone become non-linear, the noise mechanically couples to the string and/or the instrument in a way that changes the resonant behavior, the noise is somehow ...

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The difference in frequency is most likely due to the guitar going out of tune as a characteristic of background noise is that it does not have well-defined, constant frequencies, rather being a collection of all kinds of random frequencies thrown together.

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So in our results, i found that the frequency recorded in a quiet area was higher than a loud area, varying by around 5Hz. Can this be attributed to the interfering frequencies?

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In addition to the two fundamental frequencies you will also get the beat frequencies as they interfere in the microphone

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So, why some objects, even if the velocity before and after the collision seems to be the same, are louder than others? I mean, how do the different material properties enter in the phenomenon? As dmckee stated Sound is longitudinal pressure waves in the air... The impact can set up pressure waves and or ringing in the bodies themselves ...

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A typical subwoofer range might go all the way up to 200Hz. That would produce a wavelength of over 1.5m. Lower sounds will have even longer wavelengths. A lot of the energy from the sound is just going to step around objects that are much smaller in size. If that cone is small, the shape doesn't matter much. The sound isn't being reflected inside it. ...

0

This sounds like ;) it's because the object that the TV is resting on is acting as a sound conductor. Solids conduct sound better then gasses. On the 1st floor, sound goes from the TV, through the platform, through to the floor and to the ceiling of the floor below without losing much energy before being transmitted through the air. On the ground floor, ...

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According to this article (which links another article that has since become a stale link), the issue is that during ringing (and other communications between the phone and the tower) there are pulses of (relatively) high power RF transmission by the phone. Normally, this should not matter. But when an RF signal interacts with a non-linear circuit element ...

1

First of all, the effect is totally real. Here is an example YouTube video how it sounds (and a recipe how to fix it): https://www.youtube.com/watch?v=x5ruAZ4Useg I am actually getting much more melodic sounds from the speakers! ;-) And I have heard the same melodic reactions of PC speakers in many people's scientific talks and even in TV programs. ...

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The intensity $I$ of the sound is essentially the amount of energy that is transferred to the air in a unit of time. This, in turn, is proportional to the surface area $a$ of the diaphragm (twice the area, twice the column of air that is displaced). Since the area and volume $v$ are related by $a \propto v^{2/3}$, one would imagine that $I\propto v^{2/3}$. ...

3

Is it possible to measure the temperature of something using sound...? Yes, it is not only possible, it is available commercially. It is especially useful in harsh environments where conventional temperature probes might not survive. For example, TMT makes an acoustic system for measuring 2-D temperature distributions in blast furnaces: The ...

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In principle, you could detect changes on the speed of sound when passing between different zones of a fluid which have different thermodynamic conditions (i.e. different temperature and pressure as well, or density). Indeed sound propagates differently in the same fluid when different temperature, pressure or density, or any combination of them is present. ...

2

It depends what you mean by "function optimally". If you want it to be loud, it must transfer energy to the air and thus it's vibrational energy must decay rapidly. Imagine that the tines are large thin vanes (close together) so they transfer most of their energy to the air in a few vibrations. You will not hear or measure a precise frequency. If "function ...

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I was looking this up to see how common sonic books from meteors uccur. I was on my roof two nights ago finishing up a project after dark. A light caught my eye. As soon as I looked up I herd a boom right as a meteor shot derectly over my head. It was a red and white streak from north to south. It was huge for a shooting star. The boom came from the ...

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The other answers already mention pressure and heat. A bomb sets nearby bodies in motion with a speed depending on the strength of the explosion, the distance to the body, and how much surface area of the body was facing the bomb. While - as explained in the other answers - being set in motion is rarely lethal, being smashed against a wall can easily lead ...

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The blast overpressure of the explosion is a very strong shock wave which can kill humans. There are a number of ways an explosion without shrapnel can do harm to people: Rupturing of the hollow organs due to rapid compression and expansion by the shock wave. The body can get thrown through the air if a strong detonation occurs nearby. Impact of the body ...

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This is a fun question and has about 4 or 5 different factors at play: Types of forces involved: Pressure vs. Inertia Types of resistance involved: Rigidity vs. Plasticity Objects involved: Soldiers vs. Buildings Scenario: Damage from a bomb blast (energy wave) vs. shrapnel impact/penetration (kinetic collision). How damage is applied with: Blast - the ...

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Blast can definitely kill you, although it is only lethal at much shorter ranges compared to shrapnel. A building can be destroyed by 5psi overpressure while a Human can withstand up to 45psi and live. Some data here: A 5 psi blast overpressure will rupture eardrums in about 1% of subjects, and a 45 psi overpressure will cause eardrum rupture in ...

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As others have already pointed out, changing the length, and changing the boundary conditions (open end/closed end are simplest...) will change the frequency of the fundamental frequency. For an open-open pipe (like a flute where it is open at the end that you blow over and open at the first uncovered hole) the wavelength of the n^th harmonic is just ...

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Yes. The simplest change one could make to change the range is to modify the end condition. A pipe based instrument with an air reed has an open end at the air reed. The other end could be either open or closed. If that end is closed, the range goes down an octave, and the overtones change (so the tone, or timbre, changes, too). Also, changing from a ...

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Of course it is: the pitch depends on the length of the tube, not the volume. Roughly speaking, a tube 40 meters long and 1 cm diameter will have a fundamental frequency one quarter that of a tube 10 meters long and 4cm diameter. I may be off by half a wavelength here (open-ended tube resonant frequency). The bore of wind instruments both in diameter ...

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If I understand your question correctly, the answer is "yes". For most energy conversion processes, the "inverse" process exists. Typically though, as you go from one to the other, and back again, you will lose some efficiency - think of it as the universe entropy increasing at every step of the way. Specifically, with regard to your two examples: The ...

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Run this to determine which frequency range(s) you can hear http://onlinetonegenerator.com/hearingtest.html If you can hear 14kHz-15kHz then the problem is with the radio or transmitter otherwise it is your hearing I imagine that loss of hearing at an intermediate frequency would be rare especially if it is in both ears. My bet would be with poor speaker ...

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I am basing this almost completely on the comments above and my own experience of making a "tin can phone" as a kid. The string was pulled as tight as we could get it, on the basis that a loose string, i.e. no tension, would not carry the sound waves very far. But the tension in the string also makes the base of the cup vibrate, increasing your chances of ...

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I spoke with fighter pilot and instructor with a degree in aeronautic engineering. Yes both planes produce a sonic boom. But how the boom impacts you is dependent on your velocity relative to to the boom. The boom is a single percussion wave. If you are traveling with it you basically slow it down - it takes you longer to get from one end to the ...

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Researchers at the Ohio State University have shown that heat can be controlled with a magnetic field, and that it should also be possible to affect sound waves with a magnetic field. Apparently phonons, the quasi-particles associated with compressional waves and vibrations in a lattice, have magnetic properties. Here is an account of the study: ...

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Blacksmith Forum This answer is just to illustrate how one blacksmith reduced the noise level without resorting to magnets or weights. Over time, and literally being hammered every day, even a well tied down anvil must loosen it's bolts and restraining materials and start to vibrate and produce the noise mentioned. The more mass involved, the less ...

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Ok, reading up about it, here's what I think is happening. Just a guess. I think when an anvil rings, there are parts of the anvil that vibrate vigorously, and parts that are self-damping. Or perhaps there's a surface standing wave, some areas with nodes and some areas with antinodes. In any case, the vibrations happen in specific areas of the anvil. By ...

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First, check your algebra. You actually end up with units $\sqrt{\frac{m\cdot Pa}{kg}}$. Now, one Pascal is one Netwon per meter squared, $Pa=\frac{N}{m^2}$. One Newton is one kilogram-meter per second squared, $N=\frac{kg\cdot m}{s^2}$. Thus one Pascal is $Pa=\frac{kg}{m \cdot s^2}$, and if we plug that into $\sqrt{\frac{m \cdot Pa}{kg}}$ we get units of ...

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Why the rear window? The sound occurs when wind is blown across a lip: At the arrow, the wind is blowing like the air that a flutist blows across the mouthpiece - so it sets up a resonance. Now for a resonance to work, the cavity must have a sufficiently high "Q" - quality factor. The air must reflect from most surfaces, and only have a limited chance ...

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