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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What is the max frequency of sound in a given medium?

When talking about acoustic waves, medium continuity (pressure, density) is implicit. But can the wavelength of an acoustic wave be as small as intermolecular separation? For example, can ~10 THz ...
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51 views

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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64 views

Dispersion Relation for Convective Wave Equation

The convective wave equation governs the propagation of sound in the presence of mean flow: $$ \frac{D^2p'}{Dt^2}-\bar{c}^2\nabla^2p'=0 $$ or, expanded out: $$ \frac{\partial^2p'}{\partial ...
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How can I prove that antinodes are present at both open ends of organ pipe mathematically?

I know that for anti node to be formed the magnitude of displacement should be maximum at there. For standing waves in an organ pipe, the boundary conditions are such that anti nodes are formed at ...
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Physical Meaning of Over- / Underdetermined Acoustic Eigenvalue Problem

I am performing an eigenmode study on a system of acoustic ducts. The system consists of two large cylindrical volumes connected by several smaller cylindrical volumes (modeling a combustion chamber ...
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45 views

Proof that fixed points of a null field are zero

Suppose we have a scalar field $V$ (which can be acoustic pressure, or a scalar electric potential) that is a solution of the wave equation $$\Box V(x,y,z,t) = 0$$ I am wondering if a fixed ...
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60 views

sound propagation at low pressure

I am curious about the properties of sound at low atmospheric pressure. Not the speed of sound, I want to know how lower pressure will affect the distance sound will carry and the frequency range. For ...
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108 views

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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114 views

Nonsensical dispersion relations for elastic wave propagation

In an earlier question about Einstein notation, a link was provided to a medical paper which used acoustic propagation to noninvasively detect the orientation of muscle fibers. In short, muscle fibers ...
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116 views

Sound - for purposes of vibration

What is the best way to distribute noise from more than one source (I'm envisioning a system with many), within a dome, with the ground as its primary target, at optimal frequencies and volumes to ...
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107 views

Finger snapping: Maximum fingertip speed and generated pressure change

The wikipedia page for finger-snapping (or finger-clicking) describes the physics thus: There are three components to the snapping finger sound: (1) The "friction" or "sliding" sound between the ...
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37 views

Sonoluminescence spectrum

During cavitation created by sound in a liquid the collapse of the bubbles can lead to very high temperatures and pressures resulting in the emission of light - sonoluminescence. Can the spectrum of ...
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110 views

Proof of equivalence between soundwaves and phonons in large wavelength limit (Ashcroft-Mermin, ch. 22)

In chapter 22, Ashcrof and Mermin argue that the normal modes of a harmonic crystal are not only formal but precisely equal to the large wavelength limit of acoustic phonons (which sounds, of course, ...
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43 views

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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210 views

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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610 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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Reference for the reflexion of sound in connection with boundary conditions of the wave equation

In 3D, the homogenous wave equation $$ -\Delta_x u(x,t) + \frac{1}{c^2} \frac{\partial^2 u}{\partial t^2} (x,t) \ = \ 0 \ \ \mathrm{in} \ \Omega \times (0, \infty) $$ can approximately describe ...
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68 views

What is the longest distance over which echolocation is effective?

Some animals, most notably bats, use echolocation in order to navigate and detect the location and size of objects and prey. This usually takes place over short distances. What are the theoretical ...
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50 views

Is it possible to estimate the number of people in a room from a limited number of simultaneously recorded audio samples?

Note: I struggled to decide the appropriate site for this question, between http://physics.stackexchange.com/, http://avp.stackexchange.com/, http://math.stackexchange.com/, and even ...
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61 views

Harmonics of an infinite cylinder

If a hypothetical cylinder was infinitely long, could it vibrate at any frequency, since any frequency would be a harmonic of it? And (less hypothetically) if a cylinder was only really long, would it ...
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173 views

Physical difference between two different attenuation coefficient functions

The attenuation of a wave through a medium can be modeled by the Beer-Lambert Law using an attenuation coefficient. If $I$ is the intensity, and $I_r$ is a reference intensity, then what is the ...
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104 views

Can we compute the magnitude of the stress caused by sound waves on a wall?

As a follow up to this question, Could we really compute the magnitude of the stress caused by sound waves on a wall? If so, How do we do that?
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27 views

Is disturbance propagation velocity equal to wave velocity in a solid body?

How do the disturbance propagation velocity and wave propagation velocity relate to each other? To explain my question in details I will describe the following situation from the theory of acoustic ...
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Noise created due to change in Air Pressure

Background : My blower in one of the experiments is generating noise due the a short airflow path to atmosphere. The reason is due to a sudden change in pressure (high to low) the high noise is ...
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26 views

Sound frequency and power

Although I have studied physics I am not clear on this question: Given that two (or more) sound waves have the same amplitude does the power they carry depend on frequency? What about electrical AC ...
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Does the distance between tines affect sound of tuning fork?

Tuning fork handles act as clang-mode wave nodes. Therefore, I postulate that by symmetry the distance between the tines should not affect the frequency nor the volume. Let us neglect here ...
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How to arrange a 3d cymatics experiment?

Various researchers have filmed levitating polystyrene using sound waves. If i were to take 3 speakers and attempt to visualize the standing wave fields formed by the three speakers, how would i do ...
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why stack width is larger than the thermal and viscous penetration depth in thermoacoustic refrigerator?

The thermal and viscous penetration depth is smaller than the spacing in the stack:this assumption leads to the simplification of Rott‟s functions, where the complex hyperbolic tangents can be set ...
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24 views

Why does the metal mesh in an electric swatter make a whirring sound?

I have an electric bug swatter that operates on a rechargeable lead acid battery. I had one before that operated on disposable batteries and when it was turned on, it made a high pitched whining ...
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103 views

Why does hot water and cold water makes different sounds while filling a bucket from a tap

When I fill hot water in a bucket while bathing, there is a difference in the noise it makes compared to cold water. Is there any Relation between temperature of water and sound it makes during ...
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56 views

How would I calculate the frequency of the sound produced by a bowed glass plate?

I'm working on a project that involves getting a note to sound from a glass plate by bowing its edge with a violin bow. I'm trying to work out exactly what frequency I'll get from a piece of glass of ...
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95 views

Wave equation - Cases where separation of variables doesn't work

Separation of variables combined with the Fourier's theorem is the most common technique of solving D'Alembert's wave equation: $$ \Delta\Phi-\frac{1}{c_0^2}\frac{\partial^2 \Phi}{\partial t^2}=0 $$ ...
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158 views

What is the relationship between the velocity of an object and its Sound Intensity Level in an inelastic collision?

Assuming the mass, acceleration, and height of the dropped object are constant and the area of the measured sound wave is constant, would the relation be linear, exponential, logarithmic, square root ...
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92 views

Can I measure distance with sound through soil?

Can you measure distance (cca. with precision 0.1m-1m) with sound through soil. I know this is really crazy think to do, but I have this idea quite for a while. Basically I will set speakers on fix ...
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144 views

Resource on history of acoustics

Shortly: I am looking for a good resource (article, book, chapter in a book, introduction in an article...) about history of acoustics, I will be glad for any recommendations. By acoustics I mean the ...
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89 views

Reason behind “marble dropping sound” from concrete

Many people have experienced strange sounds from the ceiling of their home that sounds like marble dropping, often at night when they're trying to sleep. Currently there doesn't seem to have a fixed ...
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59 views

What does a long strip of explosive sound like when detonated?

By long, I mean something like (say) 2 km of detcord. Or perhaps multiple close spaced charges in a line over that distance, simultaneously detonated. Close up a single piece of explosive produces a ...
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120 views

Rayleigh criterion for sound and parabolic microphone

Currently I am developing a parabolic microphone for a study project. I've heard and read that the maximum wavelength of sound that the given diameter microphone can focus is determined based on the ...
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40 views

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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149 views

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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54 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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63 views

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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245 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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Sound waves travelling in air and the amount of air affected by the wave

If there is a sound wave travelling in the air, will the amount of air transported by the wave be proportional to the intensity? Here is my answer: yes, because as the energy of the wave is related ...
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Audio anomaly identification

I left an audio recorder in the forest in many different locations for fauna identification. I am collecting subjects on my audio recorder that are clearly not in the frequency range of any animal ...
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259 views

Number of wave modes in a cavity

I'm trying to calculate the number of acoustic modes that can exist in a room in a certain range of frequencies. I thought of using the Rayleigh-Jeans formula for the electromagnetic standing wave ...
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140 views

Why do the chargers produce persistent high pitch sound?

I have noticed that my Nexus Orb charger and a charger for the shaver produce some unpleasant high pitch sounds - near the fork. Why are they doing this? Does it indicate any problem with my ...
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234 views

Harmonic frequencies of electric guitar are detuned. What could be the cause?

I have tried to record some music with my electric guitar and while playing around and looking the frequencies of single strings I noticed something strange. I took the spectra of the A string and I ...
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132 views

What is the magnitude of the sound that a Helmholtz Resonator attenuates?

I know that the shape of the Helmholtz Resonator, specifically its neck shape and the volume of its cavity, determine the resonance frequency of the resonator. Moreover, the resonance frequency is ...
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Sound localization using cross-correlation

I am using cross correlation for sound localization. I have a four microphone array (arranged linearly). My problem is, sometimes the time diff found by cross correlation between a given pair of mics ...