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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Ray tracing a three-way intersection

I've been studying ray tracing in media with linear velocity-depth functions. One of the key concepts I've come across is the ray parameter, and in particular the idea that the ray parameter is ...
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55 views

Why need for 96kHz, 192kHz audio? [on hold]

Human can hear 20-20,000 Hz waves, so by Nyquist theorem it's sufficient to sample audio with 40 kHz. Indeed, 44.1 kHz widely used. But what do we need higher sample rates for? 96 kHz, 192 kHz are ...
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Bell vs. diaphragm of stethoscope for low frequency sounds

Why is the bell of the stethoscope used to hear lower frequencies if it has a smaller diameter than the diaphragm? I would have thought that a bigger diameter diaphragm could pick up lower frequency ...
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32 views

Why do empty vessels make more sound?

Why do we hear a roaring or humming sound when an empty bottle is held close to our ear ? When I hold a flask close to my ears, I hear like a sound which coming from its interior.
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20 views

Sound reduction over distance [closed]

Thank you for your responses and your time! Sorry for being unclear. Hopefully explaining what I need the answer for will clarify the question. I'm building a game engine and I'm trying to figure out ...
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4answers
119 views

Why Light isn't like an Acoustic wave?

I just wanted to know why light isn't an Acoustic wave.Is it because light wave doesn't obey acoustic properties?
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How much air needs to be displaced to generate an audible sound?

I'm reading a book where in one scene a wizard/alchemist teleports a scroll after reading. He folded the parchment carefully and muttered a single cantrip. The note vanished with a small plop of ...
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3answers
100 views

If a tree falls in the forest [on hold]

The question of whether or not a tree that falls in the forest makes a sound - if there is nothing or no one around to hear it - comes up frequently at my house. So, my question is: is there any way ...
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30 views

Sound power radiation of two monopole sources

For a fixed given electrical power to two monopole sources, producing the same frequency. Which mode, either in-phase or out of phase, will radiate the most sound power into the far-field?
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32 views

how does air pressure affect the speed of sound

How does air pressure affect the speed of sound in relation to its kinetic theory etc? I have tried searching this but i have not found a suitable answer as other websites simply related to air ...
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1answer
36 views

How to create a barrier for sound waves?

Is there a way to create a barrier so that sound waves cannot pass through? Does laser light have this ability to act as a barrier or bounce sound waves back? This came to my mind when I was ...
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15 views

What's responsible for dull or sharp sounds in a struck sintered rods?

I've sintered a number of rods from powdered oxide materials, and some of them ring clearly after being struck (not as clear as, say, a metal tube, but clear enough to hear a definite pitch), while ...
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Will a sodium bell ring clearly after being submerged in liquid nitrogen?

Lead is fairly soft at room temperature but rings clearly when cooled to liquid nitrogen temperatures. Sodium is even softer. If cooled to liquid nitrogen temperature, could it also ring?
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131 views

Is it theoretically possible to have a universe where sound travels faster than light $c$? [closed]

We all "know" nothing can travel faster than light. However, if we're allowed to tweak the fundamental constants of nature, is it theoretically possible that such an universe might exist? Update: I ...
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1answer
32 views

Why does the pitch of a container being filled with water increase? [duplicate]

I wonder about this. If you pour water in a closed tank, it makes a noise. I have noticed that as the container becomes more and more full, the pitch of this noise also increases. Why is that? I do ...
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1answer
45 views

How much of the chemical energy in a burning log is released as sound?

Firewood has energy content of about 15 MJ/kg for hardwoods. You throw one of these hardwood logs onto a fire hot enough that it burns with, say, 50% efficiency. How much of that energy will be ...
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16 views

The supersonic bandwagon

I happen to stumble upon this intriguing animation of a Tachyon, and immediately started to think about the same phenomenon, but with sound waves. I imagined a bandwagon ...
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1answer
44 views

Rubbing finger, where's the frequency come from?

When I rub my finger against a piece of rubber, and it makes a tone of 2 kHz, what is vibrating at 2,000 times per second in order to produce that tone? The rubber doesn't feel flexible enough to ...
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17 views

Source of low frequency oscillation heard in ambulance siren

I have noticed that when I am standing on the street as an ambulance passes that so long as it is sufficiently close by (within 10-15 feet, so the siren is VERY loud for this to happen), I hear a ...
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The sound of rotating helicopter blades

Why do helicopter blades make this pulsing, oscilating, slapping(?) sound? Since their movement is smooth, shouldn't the sound be a similar, constant shush, perhaps increasing or decreasing in ...
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1answer
62 views

Is a sonic boom loudest when source is at exactly Mach 1?

Please imagine this cartoonish thing: a flying loudspeaker, playing a continuous sound, with zero air resistance (i.e its moving through the air doesn't generate any whooshing sounds) is coming ...
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1answer
66 views

Is it possible to use “negative sound waves” to “cancel out” a sound to create silence?

I saw youtube videos that claimed to do this, although I'm quite certain the videos just excluded sound and lied. However, I am wondering if the physics of this is actually possible - to create a ...
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1answer
55 views

Help me understand resonance

I don't fully understand how resonant chambers work. My confusion stems from the fact that they are passive elements or "filters", yet somehow are able to "amplify" the sound. Questions: How can I ...
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4answers
49 views

Sound diffraction through a single slit

When sound waves diffract through a single slit, do they produce an interference pattern which is mathematically identical to that of light waves in the corresponding experiment?
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Can anyone provide a good exposition on acoustic impedance?

Can anyone provide a good exposition on acoustic impedance? Does anyone know of a good paper or textbook that does so? It seems like most sources kind of just start using it without deriving any ...
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2answers
54 views

Surface acoustic wave

Why does a surface acoustic wave (SAW) propagate only in the surface leyer of the solid, let's assume a semiconductor? One can create such a SAW through an interdigital transducer (IDT) as I read, ...
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1answer
51 views

Speed of sound and Break the sound barrier

What happens when plane exceeds the speed of sound? and What is the interpretation of the conical shape that appears behind the plane?
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60 views

Sound Wave interference Experiment

I was wondering, can we use two sound sources so as to create a destructive interference at the position of a recorder at home? If possible, what is the easiest way?
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Frequency dependance of sound wave reflection

Why are high frequencies reflected more than low frequencies off an 'acoustically hard' surface such as concrete? I basically understand that the amount of reflection is determined by the impedance ...
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105 views

What is the physical meaning of complex eigenvalues?

I understand the mathematical origin of complex eigenvalues, and that complex eigenvalues come in pairs. But what is the meaning of the imaginary part? In particular I refer to an acoustic problem ...
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2answers
120 views

Are there any ways to alter frequency of wave?

I want to know how can we change frequency of wave, both sound and light, and what is the nature of "changing frequency" Such as, any material could absorb and re-emit wave in another wavelength. Or ...
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18 views

Distribution of refractive index of water when applied pressure wave

I was wondering when applying pressure wave, ultrasonic sound waves, under water, how I would be able to measure the distribution of the refractive index.
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23 views

Sound vibrations for marine propulsion

I asked a similar question about bubbles making less friction on a mass moving through water, now I'm wondering of sound waves could do the same thing as supercavitation or possibly create it's own ...
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27 views

Nonlinear constitutive state equation

Between the Tait equation, and the B/A type of equation, which one is better suited to approximate the isentropic equation of state? Why B/A type is mostly used in nonlinear acoustics?
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1answer
51 views

Shock-waves, Bangs and the Speed of Sound

I was watching this video of an erupting volcano. Some Guys in the comments tried to estimate how far away the volcano is by using the delay until the "shock-wave" hits the camera and the speed of ...
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1answer
20 views

Intensity of Sound Wave

Is the intensity of a sound wave same at all the points through which the wave travels? The formula for intensity is $ I = \frac{{p_0}^2 }{2 \rho v}$. But this does not make sense to me. Shouldn't the ...
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If I shout at the sky, will some molecules reach escape velocity?

Will the sound waves, as they move higher and through less dense air, conserve energy to the point where some molecules of the rarified atmosphere attain escape velocity?
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Functional relationship of pressure and position(1d)

so today I started doing my research on oscillations in a course on advanced mechanics. The experiment was to mathematically model the speed of sound in air and experimentally prove the usability of ...
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1answer
33 views

Propagation of sound waves and monopole

While it is understood that in order for the acoustic waves to reach far field the wavelength should be less than the characteristic length of the source, I am not able to physically understand how? ...
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Calculate pressure distribution at plate surface

Currently I am having troubles calculating the pressure distribution $p(x,y)$ at the surface of a vibrating plate. I have a simply supported rectangular baffled plate which gets excited by a harmonic ...
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Is there any way a longitudinal wave can have a shear velocity component?

I am simulating the propagation of an acoustic field through elastic media. I have identified a pocket of shear stress which is travelling with a speed very close to that of the longitudinal wave ...
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32 views

What is the physical explanation for the phase relationship between acoustic pressure and particle velocity in plane and spherical waves?

I've been looking around for a decent physical explanation of the differences in the phase relationships between acoustic pressure and particle velocity in different types of waves. Mathematical ...
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25 views

On nonlinearity parameter in Nonlinear Schrodinger Equation (NLS)

While I am studying the wave propagation in fluids, the amplitude modulation seems to be governed by the NLS equation. In some of the journal papers the nonlinearity parameter, $N$ seems to be of high ...
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What the phase constant difference required for sources located at the same location?

Here is what my teacher wrote on her notes: Let's say there are two speakers located at x=0m emitting sound waves of same $\omega$ and same A. PHASE CONSTANT DIFFERENCES If A < A'<2A: there is ...
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Difficulty implementing equation describing angular response of fibre-optic hydrophone

I am attempting to implement an equation in a paper which provides an approximation of the angular response of a simple fibre optic hydrophone. The equation in question (number 19) is repeated here ...
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Equation of acoustic pressure in moving fluid: derivation

I'm looking for a detailed derivation of the equation of acoustic pressure with harmonic time dependence (of type $p(t,{\bf r}) = \psi({\bf r})e^{i\omega t}$) in moving fluid and under assumptions ...
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1answer
49 views

What allows us to distinguish between two different voices even if they're singing the same note? [duplicate]

I love Freddie Mercury. I love Robert plant. I once heard Robert Plant sing a Freddie Mercury song at a tribute concert. Plant sang the song beautifully, but it was obvious that the song was different ...
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61 views

Is stethoscope sound mono- or stereosound?

I am curious if the sound is monotonic. There are two things on my ears however. Is stethoscope sound mono- or stereosound?
3
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1answer
86 views

Giant Wind Chimes

I am building large wind chimes out of ALUMINUM TUBES with a D2 at 73.41 hertz as the lowest and two other higher frequencies of A2 at 110 hertz and E3 at 164.8 hertz. I know how to find each length ...
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Sound Source Power Formula Approximation

A sound source emits waves with a wavelength of 25 cm. 50 m away, the waves have an amplitude of 4 micrometers. It's 20 ° C outside and the density of air is 1.3 kg/m^3. What is the power of the ...