# Tag Info

3

Yes, physics covers sound. The SI unit of frequency is Hertz ($\mathrm{Hz}$), which is the same as $\mathrm{s^{-1}}$. The intensity of sound is measured in decibels ($\mathrm{dB}$), which are not an SI unit, but they are in common use and accepted by many standards bodies.

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Prime suspect is the switching power supply that generates the bias voltages for the tube. As the anode voltage is changed to increase the cathode current (the anode doesn't physically move), the power supply must work harder. Some switching power supplies operate at a fixed frequency, and so wouldn't display this behavior, but others have a variable ...

0

I appears that you are asking two questions. 1) what can generate a high pitch noise, & 2) why is the frequency of the noise directly proportional to the current applied? The general answer to 1) is, anything electromagnetic (inside or outside the vacuum tube) "loose," that resonates in the range of the mentioned frequency. The answer to 2) can only ...

4

John Rennie has provided an exact mathematical treatment of the equations behind the calculation of the speed of sound. I don't want to detract from that treatment, and of course the Wikipedia articles we both draw from provide a broader treatment; but an intuitive understanding of the 'why' has been equally helpful for me, in the past. The following is my ...

0

Your question should more accurately have been, "Why does sound travel faster in solid iron than in liquid mercury even though mercury has higher density?" Were the question phrased that way, the answer would be more obvious. At temperatures at which both metals are liquid or both metals are solid, sound travels faster in the denser metal.

3

The square of the sound velocity is proportional to the ratio of an elastic modulus to the mass density of the material.The reason why the sound velocity is usually larger in solids than in liquids and usually larger in liquids than in gases is because of the elastics constants of the material. What determines the elastic constants of a material is the ...

30

The speed of sound in a liquid is given by: $$v = \sqrt{\frac{K}{\rho}}$$ where $K$ is the bulk modulus and $\rho$ is the density. The bulk modulus of mercury is $2.85 \times 10^{10}$ Pa and the density is $13534$ kg/m$^3$, so the equation gives $v = 1451$ m/sec. The speed of sound in solids is given by: $$v = \sqrt{\frac{K + \tfrac{4}{3}G}{\rho}}$$ ...

6

"The speed of sound is variable and depends on the properties of the substance through which the wave is traveling. In solids, the speed of transverse (or shear) waves depend on the shear deformation under shear stress (called the shear modulus), and the density of the medium. Longitudinal (or compression) waves in solids depend on the same two factors with ...

1

This is an interesting question. I regret that I don't know the answer for sure, but I can say that sound does not travels in any substantially different way upwards vs downwards. Rather, I believe the answer has to do with the fact that low frequencies are carried through the physical structure differently because of where they are: things that make sound ...

0

changes in gravity will lead to changes in air pressure and density. their effect on speed of sound cancel each other out in an ideal gas, but since air is not an ideal gas the speed of sound will change. unfortunately, it is hard to say in which direction the change will go because, the direction also depends on humidity too, see here Speed of Sound in Air

1

Psychoacoustics is a fascinating and difficult field. For a simple example: many people, myself included, perceive music thru headphones as originating somewhere in the back of our skull. Same music from stereo speakers comes from "the room." So... your earplugs may well be providing a direct mechanical conductive path from jawbone, ear mass, etc. for ...

2

This sound is most likely caused by the choke coil which is inside the lamps housing. It is needed for lamp starting and operation. Starting works like this: After initially the starter circuit allows for current flow through the heaters in the tube, it interrupts the the current after an initial period. This causes a high voltage impulse to be created by ...

0

By using a Resonance Tube. :) This is obviously the laboratory version of the experiment, but with a large enough tube, it can be done in a lake, too! Each frequency needs a different resonating length. You can even try this at home; buy a small speaker which emits a certain frequency tone, submerge a pipe into water - like in the picture - and slowly ...

1

Three guesses: Light is composed of zillions of photons, elementary particles which even though have zero mass carry momentum. p is the momentum , h is Planck's constant, c the velocity of light, nu is the frequency In the link you gave one sees that the ping sound comes at a delta function in time of a lot of light. My first guess is that the ...

1

You are right that a soundboard adds no energy to the system. However, it does allow the existing energy to be converted to sound better. The greater area of the soundboard causes more air to be pushed than the string alone can, even though the displacement amplitude of the soundboard is less than the string. This exactly the same reason speakers have ...

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The soundboard resonates with the same frequencies as the source. It takes it energy form the vibrating source. As the soundboard distributes this energy over a larger volume of air, the sound is louder, but the energy is depleted quicker, limiting the time you hear the sound. Try this with a tuning fork. Hold it by your ear and time the duration 0of the ...

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The comments above that say the sound is louder because the soundboard itself begins to vibrate are correct. This is called resonance. It sounds louder because the motion of the board is mechanically more efficient at converting the energy of the system into sound waves than the string alone. The board is an effective radiator of sound energy. A louder sound ...

4

I believe it's to do with the fact that the speaker's function is to propagate pressure waves through the medium (air). So, it's mainly a mechanical concern: you want something to push air, and you do not wish to expend much energy. So it has to be light and rigid, which the cone manages to fulfil due to its shape. A plane sheet, for instance would undergo ...

3

The resonant frequency of the string only depends on its properties (tension, length, mass) But in a real instrument the complex set of frequencies that produce the note depend on how it is plucked, the stop-start motion of a violin bow, the contact with the string, friction etc.

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In physics, you are taught that any measurement needs to be accompanied by a tolerance range so that the degree of accuracy can be ascertained. How ever, in this particular situation, the equipment used to make the measurements is the same, therefore the "built in" inaccuracies (if any) are the same, so they cancel! To compensate for the difference in ...

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Yes, you are right, although the first layer already works on the second layer during compression

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In principle, there is now reason that this can't be done. There are, however, a lot of practical difficulties. You would need a high speed camera recording at something like 50,000 fps to catch all of the audio band which humans can hear. These things aren't cheap and generally can't record for longer than a few tens of seconds at such high speeds. ...

0

Propagating sound is the periodic motion of the molecules passed on through the air. So the kinetic energy of the molecules is also passed on. Temperature is merely a measure of the mean kinetic energy of all the molecules in a gas. So temperature rises only locally where the potential energy decreases, because the distance between the molecules decreases. ...

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On both the sides of the track is a speaker wich processes the sound of the gun. The gun doesnt process the sound.

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This heat or energy given by the fork is given to the next layer of air and in this way,this energy makes sound. This is the crux of the misunderstanding; sound energy is not transmitted by heat, but rather by the concerted kinetic energy of the gas movement. It is adiabatic because the heat has nowhere to go other than the gas itself. It is not ...

1

An arbitrary periodic signal can be decomposed into a sum of pure tones of varying amplitudes and phase. This is called Fourier decomposition. So, for example, a sawtooth waveform, much like that produced by a violin, has many frequency components of distinct amplitudes and phase. The loudspeaker simply reproduces the sawtooth waveform. It isn't ...

2

1500 meters in 105 seconds is an average speed of 14.3 meters per second. At that speed, a difference of 0.003 seconds means the winner crossed the finish line 43 mm ahead of the second-place finisher. Race timing is done by measuring when the leading edge of the leading skate blade crosses the finish line, and a 43 mm difference is well within the ability ...

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Is it fair to judge this speedskating race by only 3 thousands of a second? Yes, it's "fair". Not only is it according to the current rules of the event**, but also: There are at least three asymmetries that have far larger impact and are all considered "fair". They happen to start in different lanes (and must cross-over thereafter). That means they ...

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All races at this level, be they skating or running, have a speaker placed directly next to or behind each competitor. There's no sound-lag problem. As to whether we should consider sub-millisecond, or even sub-second, differences in run time is more philosophical. There's a ton of prejudice against ties. Fans want a "winner" (or at least for the ...

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At the ambient temperature and pressure (assuming atmospheric pressure), the sound speed is pretty close to $340\ \frac{\text{m}}{\text{s}}$, and it seems (from internet research) that the first contender is about $16\ \text{m}$ further away from the guy firing the gun, which comes down to a delay of about $.05\ \text{s}$ in hearing the sound if the sound is ...

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The difference is that the classical Doppler effect assumes a static background. In atmosphere, there is a marked difference between a moving observer and a stationary one - a gentle (or not so gentle) breeze. To exaggerate these effects, consider two jets flying above mach 1. If the first jet is ahead of a second, the first jet will not hear any of the ...

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The speed of sound in an ideal gas is given by $$a = \sqrt{\gamma R T}$$ Where $\gamma = \frac{C_p}{C_v}$, $R$ is the specific ideal gas constant and $T$ is the absolute temperature. Taking standard values for air, this makes a graph like this: The linear approximation is plotted by your formula, $a = 331\ \frac{m}{s}\ +\ 0.6 \frac{m}{sK} (T - 273\ ... 3 Wikipedia gives the formula$c_{air}=331.3\sqrt{1+\frac {T(^\circ C)}{273.15}}\$, valid anywhere the ideal gas law is valid. The expression you quote is given at the first two Taylor series terms.

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I don't know about your formula, but the speed of sound is proportional to the square root of the absolute temperature (for ideal gases, and approximately so in air).

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