# Tag Info

1

It's human physiology based and I am not aware of any easily implementable numerical correction. The relationship is not linear or anyhow nice. The keyword for you would be equal-loudness contour. Read more about that. Actually, if you do e.g. psychoacoustical listening tests for timbre perception, the samples are adjusted to the same "psychological ...

1

First of all, this question is more or less about the engineering and that would need another SE site. But since the answer is not complicated: If you consider sound in "common, general meaning" (i.e. something that could be percieved by an ear) then the simpliest pressure meter is the microphone. OK, there are microphones sensitive to air pressure or air ...

0

Ok, So after alot of research I am attempting to answer my own question. Current state of the art research into this exact question was published in a paper by Daisy Williams, Xiaoyi Bao, and Liang Chen under the name: "Effects of polarization on stimulated Brillouin scattering in a birefringent optical fiber" Those who want to delve in, should with regard ...

0

The analogy to Newton's cradle is incorrect. You can remove a ball from the cradle and the other balls remain in place. That is not so with most mediums. If, however, you squeeze the balls together and then remove one quickly, you will see a wave with rarefaction at the front propagate through the cradle.

0

The graph shows the displacement of matter with respect to the equilibrium position. Since some matter is displacement toward the left in the lower graph (where the arrows go down left), this means that the displacement is in the opposite direction with respect to the direction of propagation. This is why the displacement is negative and thus the reason why ...

0

As you understand from the term itself it has to do with the penetration of heat into a material. Suppose you have a sufficiently thick material (size $D$) of uniform temperature ($T_0$), where you apply a constant (different) temperature ($T_1$) at one side. Eventually, your whole material will be at this new temperature $T_1$. But before this happens, ...

0

In an unbound fluid it is sufficient to presume the adiabatic behavior (i.e. no heat transfer and "conservation of enthropy"). BUT! When we examine the flow in the nearby of walls and other real solid boundaries there is a significant energy dissipation due to viscosity, friction etc. etc. connected with thermoacoustical effects. E.g. if we have a duct wide ...

0

For a longitudinal wave to propagate you require an elastic medium. Now elastic medium has the property that once you disturb it's one portion from equilibrium, a force proportional to the displacement works on it(Hooke's Law). This force makes that portion oscillate around its equilibrium. Now in your case suppose you have given a pressure in air to create ...

-1

The key to understanding your inquiry is to see that sound has no meaning at the level in which you are asking. You have to get rid of the concept and turn it into collision or EM interaction analysis within the vaccuum. But what will collide/interact in a vaccuum to propagate sound? Nothing will interact. The terms are 0/0 and unknowable or ill-formed.

2

Well.. 1) If you were running at the speed of sound, you probably wouldn't be for long. The human body isn't designed to handle those kinds of stresses. 2) Assuming you're listening to the iPod using ear buds (in your ear) You can probably think of the air between the seal on the ear bud and your ear drum as isolated from the air you're running through, ...

0

Actually it has been observed by experiment that the actual antinode of an air column with closed-open boundary condition is actually just outside the open end, not exactly at the open end. We do not consider the effects of viscosity of air and the radiation acoustic impedance of the open end of the pipe. Hence an end correction is applied to compensate for ...

2

Just found this https://www.pa.msu.edu/acoustics/amplenv.pdf So it's a known psycho-acoustic phenomenon - we perceive the pitch of a decaying sound to be higher than a constant sound

2

This is a well known effect, and most clearly happens with hot instant cocoa which has just been mixed. Stir the cocoa while tapping the spoon on the mug, and you'll hear the pitch of the tapped spoon go down. Now start tapping while not stirring; the pitch will gradually go up by an octave or more. But, if you stir again, the pitch will go back down again. ...

2

I enjoy listening to this phenomenon as I wait for my teabag to brew. What is happening is that parts of the the ceramic cup heat up and expand. Because its shape is constrained (assuming it doesn't break), this produces a stress in the material that increases its resonant frequency (like tightening a guitar string). When it gets to Middle C, my tea's ...

1

Pressure is usually defined as the variation of the displacement from the equilibrium positions for the components of the material we are looking at. In the case at hand, sound pressure should be related to the displacements of the particles present in the air (or whatever else the medium is). If $f(x,t; x_0, t_0)$ describes the amplitude of such ...

0

I experience this too, and it's frustrating as I cannot think of any physical explanation. As far as I can see, unless there is a doppler effect due to a moving surface, the frequency must remain constant as it dies away. My conclusion is that it is a phsychological effect, ie. the pitch we perceive is affected by the volume. I don't know if this has been ...

1

(Aero-)Acoustics (among other parts of fluid-dynamics) loves the velocity potential It is something that has nothing to do with Acoustic or any other area where potentials come into play. Rather, it is a general property of fields provided certain assumptions hold. For (usually) simply connected regions whenever you have an irrotational field, that is ...

0

What you say is generally true if you consider the linear nature of resonant materials. But no materials are perfectly linear. Furthermore the frequency is not the frequency at which individual atoms resonate, but rather the system of atoms that form a resonant structure. The shape, size, etc also has to do with what frequency you get. In real structures ...

0

As docscience has already commented, it's actually not true in general. Usually the linear models in which the frequency is amplitude independent are accurate enough for many purposes but not for all of them. I would recommend you to study some weak nonlinear systems where the hybrid solution of slightly generalised linear solution are good enough. ...

1

Loudness is a subjective measurement made from testing a large population of human subjects and how they perceive different sound intensities. It, like the intensity level, is a logarithmic behavior. Again, one could use any logarithmic base. But .... Acoustic scientists have done experiments with pure tones (sine waves) and searched for the just noticeable ...

1

The basics lie in Weber-Fechner law. That would suggest generally any kind of your logarithm because the trend and tendency are the key factors. So, ok, you are basically right. In my opinion, the reasons for 10 are practical: Order estimation and readability of charts with log axes are way easier Other units as phons, sons etc. are defined using dB with ...

0

As someone working in the field I recommend to start with The physics of musical instruments by Rossing and Flectcher. There is also an extension called The non-linear physics of musical instruments. I also recommend Cremer's The physics of the violin, and Mechanics of Musical In- struments edited by A. Hirschberg, J. Kergomard, and G. Weinreich. For futher ...

2

That's what the muffler does, as you learn the first time you have a car with a muffler that gets damaged. The essential difference between gas and electric cars is that the gasoline power is derived from a carefully timed sequence of small explosions, in the pistons; the electric car does not have this phenomenon and will always be quieter for the same ...

2

Sound is carried by vibration of molecules (in air or a solid) so no you can't hear Jupiter from a distance in space. The "sounds" in the video are the changes in electromagnetic field in Jupiter's atmosphere which vary at audio frequencies, measured by radio and then played as a sound.

1

First, in the specific case of hearing, it has to be considered that the perceived loudness varies according to the frequency. So if the frequency scale of a sound is stretched, some parts of the sound may sound louder than others before stretching. For instance, if you want to focus on the bass line of a song, transpose it an octave above and it will be ...

0

Sound need a medium to travel or to propagate. In Vacuum no medium will present. So, I think velocity of sound in vacuum is zero 000.

0

Sound wave is a longitudinal elastic wave which strictly demands the presence of a material medium for its propagation from one place to another. So sound cannot propagate in vacuum (which actually has no mass and thereby no density), leave alone the speed of sound in vacuum. Moreover, if we consider the definition of elasticity, I think this concept does ...

4

Yes, you're wrong. Sound waves are small compressions (oscillations) of an elastic medium, travelling through that same elastic medium (as a wave). Air, liquids or solids are typical elastic media through which sound waves can travel. Vacuum however contains no matter and cannot sustain sound waves at all. Watch this video on a bell in a vacuum jar.

0

Sound travels around 343 metres/s (1100 ft/s). If a sound echos back to you in 2 seconds, the canyon wall producing the echo would be exactly that distance away (the sound takes half the time to get to the object and half the time to return). The distance for a canyon wall with a 2-second echo delay would be 1 sec × 343 metres/s or 343 metres (1100 ft). So ...

0

You are right (assuming the echo goes from bottom of the canyon, which was not specified). Sound had to travel from top to the bottom, get reflected and travel back, hence the time it reached the bottom is half of the total time. The other teacher's note is surely irrelevant.

0

Here are some ideas to be considered: What was the position of the source, microphones and starter at the beginning of the experiment? To get a reasonable data the source should be already moving when passing the first microphone. Do you have a signal long enough (in time) Fourier analysis to be precise? Did you try that on more frequencies? If you don't ...

2

Air nearest the water is cooler than air farther above the water. As sound travels slower in cool air, if sound waves from warmer air enter the cooler layer they are refracted downward toward the ear of someone in a boat. If the water is calm, its flat surface allows sound waves to travel unobstructed and to reflect from the surface. Instead of ...

1

Yes, I think so. Since we don't have the source behind our backs, we will "meet" the sound and be able to hear it. When we pass the stereo, we will be able to hear the sound of the "stereo history" (i.e. already radiated) but not any "new one" (radiated post our flyby).

1

Sound wave are classical objects. There is no wave-particle duality there. The choice of time window will affect the precision with which you can measure your frequency (This is what comes out of Fourier analysis.) as well as the integrated intensity of sound that you measure. For a given time interval (assuming that you trumpet is loud enough so that you ...

0

In my opinion (and I state that not for my ego but to express that it can include mistakes), you take it a bit wrong way. Psychoacoustical point of view: There is no such thing as a strict frequency or time domain. In our physiology and connected cognitive processes you can't think in terms of Fourier transform. For example: yes, it takes some time between ...

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