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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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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Why do smaller wavelengths image particles more clearly when the particle size is already big?

Yesterday I scanned an ultrasound phantom that had cylindrical inclusions (1.5mm diameter). When I boosted the ultrasound frequency from 3MHz to 4MHz, these inclusions became much more clear. I ...
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Refraction of Sound Waves

When sound waves go from air to water what will happen to the wavelength and the angle of refraction? I used the approach that we apply to light waves and concluded the wavelength will decrease and ...
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What causes the buzzing sound when the electricity changes into heat?

When I turn on any kind of electric heating (kettle, cooker, heater, ...), it keeps producing a constant buzzing sound. What is the exact cause of that sound? Do the electrons of the electric ...
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Optimum “fur” dimensions for absorbing ultrasound at a given wavelength?

By "fur" I mean an array of bendable fibres aligned vertically on a substrate. The ultrasound hits it at an oblique angle. Is there a spacing that will provide optimum absorption? A basic thought ...
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Humans Voice Frequency? [closed]

Do all human beings have a different voice frequency like they have different finger prints? as all of us are unique so probably our vocal folds make different vibrations while saying a same word that ...
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Natural acoustic modes of a open-open converging or diverging duct

The fundamental frequencies of air columns depend on the length of the column, the speed of sound and the boundary conditions. For a straight duct the natural modes are $f = \frac{n ~c_{sound}}{2L}$....
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Is it possible to low pass filter the amplitude of a sound wave?

Is it physically possible to block or attenuate noise above a certain amplitude, but leave other lower amplitude noises unhindered?
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Can you have a problem with a Dirichlet boundary condition but with waves that reflect off the boundary?

Say we are looking for a solution to the Helmholtz equation $$(\Delta + k^2) u = 0,$$ in in the upper half space ($y > 0$) in 2D with a Dirichlet boundary condition on the $x$-axis, that is, $u(x, ...
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How does sound propagate through a mesh structure?

I am assuming that the material and holes are approximately the same dimensions and also similar to the wavelength of the sound. In my case, around 2mm. How does varying those dimensions affect the ...
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What causes a materials distinc sound?

If a brass,iron and glass object emit a similar ring when struck yet all 3 objects are different in size,weight and structure, What do these 3 objects have in common to emit such a similar sound?
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Is a change of a few decibels in loudness of a sound noticeable?

What is the minimum change in loudness (units:decibels) that the human ears and by extension the human brain can recognise?
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What is the player's role in the functioning of a theremin?

I recently see a video on how the theremin works, and wasn't satisfied with the answer. I watched around, but they all seem to give the same explanation. A diagram as below is given, and it is ...
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Derivative with respect to a difference of independent variables

I am dealing with an equation from nonlinear acoustics (Khokhlova-Zabolotskaya-Kuznetsov equation) where a strange term (for me as a mathematician) is used. The equation looks like this $$ \frac{\...
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An experiment to show sound waves

My 6 year-old son asked me to explain the sound barrier. I think I'm ready to explain, but I wanted to know if I could add a little homemade experiment to show visually how soundwaves are generated. ...
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How much time will for the observer last sound of thunder? [closed]

We have height of the cloud 5 km. The observer stands 20 km away. The speed of sound depends only on the temperature. $C=a\times\sqrt T$ Temperature on 5 km is $-33^o C$ and on the ground $7^oC$. ...
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Is the speed of sound in air constant?

In Optics lecture we took a formula for the speed of a wave which is: $$ v=\frac{\omega}{k} $$ where $\omega$ is number of complete vibrations per second: $$ \omega=\frac{2\pi}{\tau} $$ and: $$ ...
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Conservation of energy in a sound wave

I have two ultrasonic transducers, an emitter and a receiver, and I'd like to know how the energy of the spherical wave is conserved. I guess the energy is proportional to its amplitude and it ...
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100 views

Why are two speakers at the same volume and distance not twice as loud?

If I have two identical speakers facing me which are adjacent to eachother, playing the same music at the same volume, would it be any louder than having just one speaker at the same volume? If not, ...
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Rarefaction/compression events detection using time resolved sound measurement

I had a question about sound measurement in air using a B&K condenser microphone. In the acquired time resolved sound measurement signal I can see both negative and positive voltages/ pressure ...
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60 views

When does the shock occurred?

I'm between this 2 conditions that when does the shock occurred over an airfoil. When the speed of point of an airfoil reach to sonic velocity of environment. When the speed of point of an airfoil ...
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28 views

Confusion about the shock growth

I am studying Hamilton's & Blackstock's Nonlinear Acoustics. One of the essential phenomena associated with a finite-amplitude (unidimensional, planar) sound propagation is building the shock due ...
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Pressure Inverting Reflection of a Sound Wave

How would the frequency and energy of a pressure inverted sound wave compare to the frequency and energy of the original sound? Would it sound any different?
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Sound pitch of glass with water

I have a glass (made from glass) at room temperature. I poured very hot tea in it and started stirring. No extra tea is poured in the glass. When hitting the glass with the spoon, I noticed the ...
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Helmet to helmet in vacuum - can we talk?

Usual SciFi scene. In a spacesuit, in vacuum, with the comms out for some reason. They want to talk, so the butt helmets together so sound can pass through. Questions are: a) Would it really work in ...
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Why don't we hear sound reflecting from buildings, mirrors, etcetera?

We can see buildings, doors, cars etc. as light falls on it gets reflected to us. but why doesn't the same thing happen with sound? I mean why don't we hear sound reflecting that much?
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Liquid wave faster than sound in the above gas: possibility implications

I recently heard that tsunamis (meaning "harbour wave") can travel over 800 kilometres per hour (500 mph), not so far from the speed of sound in the air. May it happen, in general, that a wave in a ...
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What would happen if we try to emanate sound waves from a conic surface? [duplicate]

Say we want to emanate sound waves through a conical surface, what would happen at the tip? How would the waves be?
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Can Doppler Shift be used to calculate speed of an observed object?

Thanks for looking. Just musing over an idea this afternoon: if I had a radio controlled plane, I could obviously calculate its airspeed based on pings and the known speed of sound if it was ...
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A question about different intensity of a sound source in a room

A few days ago, I entered a temple room with dimensions (which are only approximate) shown below in the diagram. There was a low humming sound of the exhaust fan which was at a height of approximately ...
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Standing wave confusion

To form a standing wave, two coherent waves must travel in opposite direction. But is it it necessary for them to have the same amplitude and no phase angle difference?
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108 views

Do gravitational waves travelling through a medium produce sound?

Say Alice decided to orbit dangerously close to a couple of black holes circling each other. She is in a heavily enclosed astronaut suit, as is Bob, who is floating much further away. Assuming Alice ...
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Is it possible for a harmonic to be louder than the fundamental frequency?

Using most sound equations, it is quite clear that increasing frequency decreases amplitude, but is there any example where this is not true?
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Why would a decreased length mean a higher frequency of sound?

This is in terms of the Water Bottle Lab: adding water (effectively decreasing length) to a bottle and finding its fundamental frequency at different lengths/amounts of water. I understand what ...
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When you push a stick will the end of it respond later than the beginning? Is so what is the fastest material and what forces are involved?

Normally when two people hold a long stick the receiving person would feel at the same time the stick moving when the first person gives the stick a push. But is that in reality exactly the case? ...
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If there are two different standing waves of different lengths in an open air column, what frequency would resonate?

Suppose I am playing a hypothetical woodwind instrument with both ends open. Somewhere along the length of the tube is a hole, which cannot be at or near the exact center of the tube for the sake of ...
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Speed of light and sound

Speed of light is universally constant so in denser media its collision increases so effective speed will decrease so how we distinguish this effective speed and $3\times10^8$ m/s. But why sound ...
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What determines the size of features on the CMB?

I have been learning about baryon acoustic oscillations. I am however confused about the size of the features as seen on the CMB. It is claimed that the largest structures have a size given by the ...
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About speed of sound?

Even though Speed of sound at room temperature is very large equal to 342m/s yet it does not cover that much large distance when we speak. What are the conditions at which sound really travel 342m in ...
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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 t^2}+2\...
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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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Baryonic acoustic oscillations: Why are there standing waves in the CMB?

On page three of the following http://www.quantumfieldtheory.info/CMB.pdf, Klauber talks about the formation of standing waves from acoustic vibrations in the early universe. He claims that they form ...
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Is it possible to create sound focus in a room?

Is it possible to create a place, where sound, produces by room's environment, is loud in one or several points, but barely audible in other parts of the room?
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Why are sound waves adiabatic?

I want to know why we can treat sound waves as an adiabatic process. Precisely, I know that pressure and density vibrations occur so fast that molecules have no time to exchange energy (I might be ...
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How can you make harmonics on a string? [duplicate]

For an oscillating string that is clamped at both ends (I am thinking of a guitar string specifically) there will be a standing wave with specific nodes and anti-nodes at defined $x$ positions. I ...
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Is the velocity with which molecules of the medium oscillate same as velocity of the sound in that medium?

I wanted to know that under sound field applied molecules of the medium oscillate with some velocity in the direction of sound propagation. Is this velocity same as velocity of the sound in that ...
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Why is sound intensity defined as the product of pressure and particle velocity?

The intensity of a sound wave is defined to be $$\vec{I}=p(x,t)\vec{v}(x,t)$$ I can see that the units on either side of the equation balance, but I can't find a derivation online that shows why $\...
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Is the fact that sound travels faster in metal than in water related to the fact that hitting metal is louder than hitting water?

I am mostly a mathematician but have some physics background. I was tutoring high school physics, and we were covering the speed of sound in various mediums. He noticed that the speed of sound in ...
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Book recommendations on physics of music and musical instruments [duplicate]

I am pursuing a degree in Mathematics and have a strong interest on music. I would like to understand the physical basis of how is music made. Does someone know some bibliography on this subject?
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Is the speed of sound observable without tools?

Many times, I had already had the impression that what I was hearing was desynced from what I saw. Could this be caused by the speed difference between light and sound? Or is sound still fast enough ...