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Questions tagged [acoustics]

Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. Applications of acoustics are for instance the audio and noise control industries.

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4
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1answer
268 views

Total internal reflection of sound

Does sound experience the total internal reflection from a boundary of two materials, say, aluminum and copper? The Freshnel formulas for light depend on polarization. However, sound typically is not ...
3
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1answer
135 views

Do these PR Letter authors suggest sound transports mass, or only that it can be a source of gravitation?

Question: Do the authors of this PR Letter suggest sound transports mass, or only that it can be a source of gravitation? The Phys.org article More evidence of sound waves carrying mass says: ...
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3answers
132 views

Can a sound wave begin with rarefaction?

Some digital recording samples (audio files) of recorded acoustic sounds present sound waves which begin with rarefaction. Is this an actual phenomena that can occur or is it a result of sound ...
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1answer
22 views

How loud does a sound need to be to make pressure waves detectable by a camera?

I've seen Veritasium's video that describes how sound can be picked up by a camera by observing small movements of objects sensitive to pressure changes (bag of chips, aluminium foil, paper...). That ...
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4answers
3k views

If all harmonics are generated by plucking, how does a guitar string produce a pure frequency sound?

A guitar is a plucked instrument and it is played by plucking a string at an off-centre point fixed at two ends. In general, Fourier analysis tells that all harmonics (the resonant frequencies of the ...
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1answer
49 views

Sound Waves Moving Large Objects?

I recently read an article over using sound to move/levitate objects in mid air. Which is basically using sound to go against/defy gravity. For Many years Physicists have been able to move smaller ...
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2answers
2k views

Why does a metal block make a shrill sound but not a wooden block upon hammering?

When hammered, a metal block makes a shrill sound but not a wooden block of identical shape. Is it that the wooden block vibrates with lesser frequency than the metal block? If so, why is that? Also ...
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2answers
501 views

Yi's Bell sound and how it relates to temperature?

Yi's Bell is an ancient chinese musical instrument that plays different sound frequencies when its heated than when its in room temperature. My question is Why does that happen? Why does higher body ...
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1answer
28 views

Does speed of sound in of air change if it is enclosed vs. open air?

To calculate the velocity of a pressure wave (sound) in a fluid, I came across the equation c = sqrt(K/p) where K is bulk modulus and p is density. My question is, if density of air stays constant, ...
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0answers
22 views

Loudspeaker attached to cylinder - effect on speaker SPL?

I have a loudspeaker that is facing into a long cylindrical piece of PVC pipe of length $L$. The loudspeaker is sealed in so that no air can escape around the edges. The pipe is open at the other end. ...
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1answer
62 views

How to calculate acoustic impedance of a megaphone

I'm working on a physics problem that asks how a passive megaphone (simple cone shape) can optimise the transfer of the human voice, compared to not using one at all. I understand that some of this is ...
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0answers
13 views

Dependence of heat transfer rate on acoustic boundary layer thickness

I have generated a sine wave acoustic signal of constant amplitude and different frequency (i.e. 50Hz to 250Hz). At low frequency i am getting higher evaporation rate. However, at low frequency ...
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2answers
47 views

Loudspeaker attached to cylinder - closed or open?

I have a loudspeaker that is facing into a long cylindrical piece of PVC pipe of length L. The loudspeaker is sealed in so that no air can escape around the edges. The pipe is open at the other end. ...
2
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2answers
62 views

Why are there these other “harmonics” (violin-specific terminology) in violins?

I've often read explanations of how standing waves form on the string of a violin and their harmonics but there is another phenomenon I've never seen explained: When you play certain notes, musicians ...
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0answers
33 views

Are sounds louder at night, in the winter? [duplicate]

Surface temperatures of -40C and +40C are not unheard of in habitable areas on Earth. That's a variation of over 30% in density (for a given barometric pressure). Does that mean that for the same ...
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0answers
123 views

Is this derivation of the Doppler effect for sound waves valid?

I was recently considering how to justify the formula relating to the Doppler effect for sound waves to a group of eleventh grade students who are likely encountering it for the first time. The ...
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2answers
54 views

Why will a guitar string “ring” when I resonate my vocal chords at the same pitch as the string?

From a resting state, a guitar string will begin to ring as I resonate my vocal chords. If I make a fairly loud, and high-frequency "oo" sound at 440hz, then the A string on my guitar begins to ...
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1answer
23 views

How or where I could experience sonoluminescence in daily life?

Sonoluminescence is a known phenomenon, even if a conclusive explanation for its origin is not given. I wonder if I could ever hear and see sonoluminescence somehow or somewhere in daily life, or if ...
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1answer
81 views

Where does the sound we hear from short circuits come from?

Title is self explanatory. Whenever I see or watch a short circuit happening, there is always a humming/buzzing sound going on (e.g., the sounds we hear from this short circuit compilation video). ...
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0answers
24 views

SOUND WAVES :: organ pipes [duplicate]

Why doesn't sound wave escape in a open end pipe, why does it reflect again at open end of organ pipe when it can just move outside.
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3answers
89 views

Sound Waves and the Boltzmann Distribution

Imagine a sound wave traveling linearly in a given direction through a monatomic ideal gas. Based on gas laws and the wave equation, we have that the wave should travel, in that given direction, at a ...
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1answer
56 views

What determines the speed of sound in different mediums?

So, the speed of sound is 340 m/s in air, but it’s much higher in water. I’ve gotten the explanation that the density of a medium determines the speed of sound in the medium. The more dense, the lower ...
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0answers
29 views

Dopplar Effect with Relative Velocities

My understanding of the classical Doppler effect formula was that the velocities (of the receiver and source) would be relative to the medium in the following formula: However, Wikipedia has an ...
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2answers
40 views

Why do sound waves hang together when traveling at different speeds? (i.e., being refracted)

I've heard that if a cold air layer exists above a warm one, sound may be refracted upward, causing it to miss hearers that otherwise could hear the sound. My understanding (which may not be correct) ...
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3answers
95 views

Why, in an open or half-open pipe, must an open end of a standing sound wave have a pressure of zero?

I believe this question was asked in some form before, but I'm not clear on the answer. If a sound wave must equal air pressure when it exits a tube, why is it possible that at many points after the ...
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1answer
31 views

Can sound with lower frecuency without overtones produce standing wave of higher frequency?

I read that resonance appears if frequencies are equal. What if vocal cord produce only pure tone without harmonics, will voice still have overtones? Or will sound of guitar with only one string ...
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0answers
25 views

How does one deal with 2 waves to view their beats graphically?

Two tuning forks have frequencies of 480 Hz and 512 Hz respectively. The beat frequency should be the difference, which is 32 Hz. Now I want to see this graphically. I modelled these two waves as ...
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5answers
1k views

If eardrum vibrates when hit, why don't we hear the air in the room that is continuously moving? [duplicate]

The eardrum is pretty thin.Therefore it should be very sensitive to movement.So, why don't we hear the air that is constantly moving.My guess is that the force of air pressure is not enough.Maybe I am ...
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1answer
30 views

Acoustics - tiny ultralow impedance speaker? [closed]

Here's a theoretical question that hopefully someone will be able to shed some light on. Apologies if this is the wrong forum, I figured the electrical engineering community would be more into ...
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2answers
61 views

How can we recognize the sound of two different sources?

Why when 2 or more persons are speaking we can identify the sound source ? How the superposition of the waves make the waves still be heared as they were alone ?
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2answers
167 views

Why don't I hear beats from a violin when playing two strings at once?

If I use a bow to play two strings at once on a violin or other string instrument, I don't hear beats occurring. Why's that?
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1answer
35 views

Maximum of a sound wave [closed]

I have a question regarding an undergrad problem, and I thought it was going to be easy, but apparently I am missing some key element. The exercise is the question IV-9 of the french Geipi-Polytech ...
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0answers
43 views

Are sound waves in the cochlea transverse or longitudinal? [closed]

Soundwaves are typically shown as transverse in the cochlea, but surely they would be longitudinal? Are they shown as transverse because its easier to draw only?
48
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2answers
9k views

How do we get supersonic bullets?

I recently answered a question on the WorldBuilding forum about grenades and bullets. One of the things that came up was that I argued smokeless powder in a rifle round could detonate, but was ...
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1answer
81 views

First Order Approximation of the Navier-Stokes Equation: Order of Magnitude of the Gradients of First-Order Fields

I am currently working on a project in acoustics and I am studying first and second-order approximations to the Navier-Stokes equation. I have been reading the book 'Theoretical Microfluidics' by ...
3
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4answers
453 views

Using sound to change the color/wavelength of light

Is it possible to use sound to change the wavelength of light, and therefore its perceived color? In an effort to rephrase my question from the information gained in the first answer, would it then ...
8
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3answers
502 views

Why does sound behave differently in water than in air?

I noticed in some experiments at home that sound does not behave the same in water than in air. Is there a good scientific explanation to this? I noticed that the sound sounded distorted in water but ...
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0answers
44 views

Fourier Coefficients

Suppose i've a two voice samples v1 and v2. Comparatively voice v1 is louder than the v2. If both the voice is spoken by the same person.(Spoken normally as he speaks) Is it good to state the ...
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1answer
49 views

Confused over the complex term in the simple harmonic wave equation

I am trying to derive the general equation of Lamb wave. My book says that $$y = A\exp(i(kx−\omega t))$$ is the general equation of simple harmonic wave propagating in +ve $x$ direction. but I am ...
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1answer
43 views

Could we interpret search for the Pitch as a process similar to the collapse of the wave function?

According to Wikipedia: In quantum mechanics, wave function collapse is said to occur when a wave function—initially in a superposition of several eigenstates—appears to reduce to a single eigenstate ...
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1answer
64 views

sound waves , standing waves,wind chimes [closed]

I don't know how to approach this problem. It's been bothering me for months. The answer seems to be the rod with shortest length
1
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1answer
165 views

Apparent frequency as function of distance

So the Doppler effect says that the frequency of sound changes due to relative motion of source and observer. My question is if there any expression that tells how the apparent frequency changes in ...
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0answers
21 views

How does a sonic jet attenuate a sound wave?

Let's assume air flows through a pipe and exits into free atmosphere. The atmospheric pressure is below the critical pressure of the flow, hence the gas is accelerated and a sonic jet forms at the ...
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0answers
31 views

How to measure wave vector from complex pressure?

I want to plot the dispersion relation in comsol for an acoustic waveguide. I am working in pressure acoustics, so my dependent variable is pressure. Comsol treats pressure as a complex number. How ...
3
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1answer
58 views

Sound emitted by droplets hitting a liquid surface

when a liquid jet (e.g. water) hits a water surface sound may be produced if, due to Plateau Rayleigh instability, the water jet has formed into droplets. But what exactly causes the sound? Is it the ...
2
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0answers
42 views

Strange sound of low frequency produced from 2 steel balls

When two steel balls collide, or any metal objects collide, a high frequency sound is produced. However, what was strange is that when I held two metal balls in my hand, and moved them around, it ...
0
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1answer
29 views

How does an magnetic resonance guided focused ultrasound (MRgFUS) machine work?

As a medical application, magnetic resonance guided focused ultrasound (MRgFUS), is new I the treatment of some parkinsonian diseases, prostate cancer, none problems, and more. However, I am not sure ...
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0answers
43 views

Laser creating weird patterns on screen when reflected from a vibrating membrane

Me and a few friends were doing an experiment today in which we took a membrane stretched over a speaker, and a small mirror in the center of the membrane. We reflected a laser off the mirror on a ...
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1answer
46 views

Why can I hear the treble sounds through a speaker, such as on my phone, better than I can with headphones?

I'm not sure if this is related to my hearing loss, or if anyone else has noticed it, but I find it easier to hear higher frequency sounds coming out of a speaker that I hold up against my ear versus ...
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2answers
776 views

How does the thickness of a string affect the frequency?

I've notice that thicker strings have lower frequencies, but is there a specific relationship between theses two?