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.

323 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
7
votes
0answers
142 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 ...
4
votes
0answers
76 views

Are sound waves in fluids also Goldstone modes?

One usually says that sound waves in a crystal, ie. phonons, are Goldstone modes of the broken translation symmetries. However, fluids have sound waves and also translation invariance. In fact, it's ...
4
votes
0answers
62 views

Pitch change opening thermos flask

If I return to my (closed) thermos flask for some more coffee, I hear a ringing sound as I open the flask (it is all metal), but the pitch of the ring increases as the sound fades - duration on the ...
4
votes
0answers
91 views

Using convolution to simulate acoustic dispersion in shallow water

Background I'm a marine biologist who's trying to wrap my head around shallow water propagation. I'm interested in how acoustic dispersion (as described by Pekeris' waveguide) alters how sounds ...
4
votes
0answers
61 views

Why do scattered waves vanish when the wavenumber of the incident wave is an eigenvalue of the interior Dirichlet problem. Where has the energy gone?

I normally work with numerical computations for wave scattering, but I am now trying get a better understanding of the physical processes underlying the theory, in particular what happens to the ...
4
votes
1answer
174 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 ...
3
votes
1answer
67 views

Is there a way to inspect thin metal weld (2 mm - 3mm) by ultrasonic testing?

I am working with an ultrasonic device to inspect welds. So far, I have learned that the minimum thickness of the metal sheet for this inspection is 6mm - 8mm. But the product of mine has 3mm thick ...
3
votes
0answers
83 views

Indicator of the acoustic level in near field

Usually in acoustics, it is assumed that what we hear is the acoustic pressure. In far field - when the distance to the source is larger than the size of the source and than the wavelength - one has $...
3
votes
0answers
77 views

Fluctuation-dissipation theorem for the acoustic equation

Recently I discovered a paper by R. Snieder on the extraction of the acoustic Green function from cross-correlations of the acoustic noise. What differs this paper from other papers on the subject, is ...
3
votes
0answers
167 views

Quarter wave matching layer of a piezoelectric transducer

I am trying to understand the quarter wave matching between two layers of impedance $Z_1$ and $Z_2$, where $Z_1 > Z_2$. I can understand the electrical transmission line analogy of matching layer ...
3
votes
0answers
301 views

Using train horn echo to measure distance?

This is not homework... it's way too hard! It's actually just a really intriguing problem I've wondered about for years while listening to trains echo through the mountains. Here's the simplest ...
3
votes
0answers
212 views

Could sonoluminescence be the result of the Casimir Effect?

My question concerns Sonoluminescence. I was amazed to learn that collapsing cavitations in liquids generate temperatures greater than 20,000 Kelvin. Is it possible that the vast amount of energy ...
3
votes
0answers
64 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 (non-...
3
votes
0answers
85 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 ...
3
votes
1answer
518 views

How to get the pressure amplitude at any spatial point?

Working on the pressure equation from the linearized euler equations, I stumble across a very simple problem : How, from the pressure solution of the specific equation (see http://www.acs.psu.edu/...
3
votes
0answers
168 views

Sound waves and chromism?

I am definitely not a physicist, but I have a question related to Physics so I thought I'd give it a try. Please excuse my ignorance. :) I am somewhat familiar with the changes in color caused by ...
3
votes
0answers
70 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 ...
3
votes
0answers
147 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 ...
2
votes
0answers
39 views

Fate of acoustic phonons in incommensurate charge density wave states?

In most standard exposition of (the mean-field theory of) charge density wave (CDW), phase and amplitude fluctuations are introduced as the collective excitations. Kohn anomaly in the acoustic phonon ...
2
votes
1answer
53 views

City songbirds sing in higher pitch?

In this What I've Learnt Youtube video How Did Language Begin starting at the marked point, the author claims that the songbird in the city uses higher pitch to reduce echo bouncing. He later also ...
2
votes
0answers
24 views

What is the criteria that determines the difference between a plate and membrane, with material considerations?

So according to Venstel and Frauthammer in their 2001 book, the criteria for differentiating between rigid plates, thin plates and membranes is $a/h$ where a is a typical in-plane dimension (the ...
2
votes
1answer
35 views

Apparend frequency when the source travels with the speed of sound

Let's assume an object travels with the speed of sound towards a stationary observer in a straight line. Let's say the frequency emitted by the jet is $f,$ speed of sound is $u. $ and the speed of jet ...
2
votes
1answer
74 views

Harmonics in a tube closed at one end

I have been learning about sound and how a tube closed at one end only seems to have odd harmonics. However, I have found that although clarinet follows this and plays only odd harmonics, saxophone ...
2
votes
0answers
46 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 ...
2
votes
1answer
273 views

Are acoustic phonons always the lowest energy vibrational modes in solids?

In solids with unit cells containing more than one atom, the normal modes show acoustic and optical branches. The number of optical branches is proportional to the number of atoms in the unit cell, ...
2
votes
0answers
179 views

Negative mass of sound waves?

I have just discovered multitudes of pop science articles promoting a recent arxiv paper, "The mass of sound"[https://arxiv.org/abs/1807.08771 ], which claims that sound waves have negative ...
2
votes
1answer
49 views

What are all the possible ways to achieve acoustic resonance in a cavity?

If one were to observe acoustic resonance in a cavity (semi-closed volume of space) what is the complete list of potential hypotheses as to the cause? In my limited experience I can list the ...
2
votes
0answers
229 views

What is the “sweeping velocity” of a turbulent flow?

Background: While reading Rubenstein and Zhou 1997 I encountered an unfamiliar term, "sweeping velocity". To quote the authors (pg. 3): ...the sweeping hypothesis makes the decorrelation depend ...
2
votes
0answers
121 views

Deriving the longitudinal sound wave from the transverse string vibration

I am trying to derive the longitudinal sound wave (i.e. either the pressure $\psi_P(x,t)$ or the displacement $\psi(x,t)$, where both $\psi$s are in the direction of $x$) produced by the vibrations of ...
2
votes
0answers
74 views

Odd sound from a windmill

I went to a field of windmills this morning at sunrise and as I got close to one of them, almost underneath it, I heard a very odd sound coming from the windmill. It sounded like the tearing sound of ...
2
votes
0answers
80 views

How does a “Haskell Resonator” work?

I would like a simple explanation of how a "Haskell Resonator" works. You may assume that I understand the Wikipedia paragraphs on open and closed resonator cylinders. Exactly how does placement of ...
2
votes
0answers
98 views

Intensity of an ultrasound beam?

I am working through question 9.1 (link to Google Books) of 'Fundamental Physics for Probing and Imaging' by Wade Allison. The question involves finding the varies quantities (such as pressure ...
2
votes
0answers
74 views

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 ...
2
votes
0answers
465 views

Best frequency for underwater transmission

What is the best frequency for a high data rate of underwater transmission? I have read that the threshold of hearing underwater is around 170 to 180 db. Can this be useful in calculating the best ...
2
votes
0answers
153 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, ...
2
votes
0answers
77 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 ...
2
votes
0answers
93 views

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 ...
2
votes
0answers
681 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 ...
2
votes
0answers
147 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 ...
2
votes
1answer
381 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 ...
2
votes
0answers
88 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 https://physics.stackexchange.com/, https://video.stackexchange.com/, https://math.stackexchange.com/, and even https://...
2
votes
0answers
97 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 ...
2
votes
0answers
200 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 ...
2
votes
0answers
119 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?
2
votes
1answer
245 views

Two sonic booms colliding

If I theoretically created an experiment where I could create two sonic booms in directions such that the sonic "nose" is facing each other; what would happen? more specifically: Lets suppose I have ...
2
votes
1answer
91 views

How can some fireworks be loud enough to feel the concussion in my chest without hurting my ears?

I attended two fireworks displays this Independence Day, and I noticed an odd phenomenon when comparing them. I was several hundred yards away from the first display, and I could feel the concussion ...
1
vote
0answers
42 views

The relative velocity of sound waves in Doppler effect

Let speed of sound in the medium be $v$ when the source is at rest w.r.t the medium. In the case of the observer moving towards the stationary source with a velocity of $u_1$, the speed of sound ...
1
vote
0answers
17 views

Is there a formula that links between emited sound level (dB) and specific heat capacity?

I'm doing an experiment on soundproofing and seeing how different materials with different specific heat capacities affect the level of sound emitted from a music speaker. Each material is formed into ...
1
vote
0answers
41 views

Impedance in terms of position in a driven, open standing wave tube at resonance

I have a cylindrical tube of length $L$ and radius $a$ with a loudspeaker sealed at one end ($x=0$) and open to the atmosphere at the other end ($x=L$). The tube is being driven by the speaker at a ...
1
vote
0answers
37 views

Solving integral of spherical means

The solution of 3D wave equation is given by Kirchhoff's formula as $$u(t,\mathbf{r}) = \frac{1}{4\pi c^2t^2}\int_{\partial S(\mathbf{r},ct)} \bigg[u_0(\mathbf{r'}) + (\mathbf{r'}-\mathbf{r})\cdot \...

1
2 3 4 5
7