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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Why does scratching a blackboard gives such a painful noise?

I think we all have heard that terrible sound coming from scratching a blackboard with your nails. How is it produced? Has it something to do with the length of our nails?
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Time it would take for sound to travel between moon and earth? [duplicate]

Neil degrasse Tysons documentary series the Cosmos, he mentions that we actually see the moon one second later than it actually is due to the distance of the earth and the moon and speed of light ...
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26 views

Solution of Burgers' equation in preshock region

According to Hamilton's & Blackstock's Nonlinear acoustics (Section 4.5.4) the solution of Burgers' equation of the form: $$ \frac{\partial P}{\partial \sigma} - \frac{1}{\Gamma}\frac{\partial^2 ...
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How can the amplitude of the same acoustic wave be different in a interferometer?

I came up with an exercise on Halliday Resnick Krane that asked a question which consfuses me. I premit that I do not look for a solution of the exercise but for suggestions only regarding the ...
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light and sound speed [on hold]

why is the speed of light faster in water than it is in air? And why is the speed of sound slower in liquid than it is in air? Is its difference is related to wave's appearance? like transverse wave ...
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35 views

Speed of sound in different states

Consider a gas at very low temperature(lower than critical) and pressure . Upon increasing pressure it will transform to liquid state. I know that speed of sound is independent of pressure, and also ...
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Doppler shift and Galilean relativity

Doppler shift has different forms if the observer or the source are in motion. I consider Doppler shift in the case of sound. I tried to find an answer on the non symmetry of Doppler effect, ...
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Acoustic beats interference vs. path difference interference

I'm trying to understand the differences between two kinds of waves interference. The first one is a time-interference, only due to frequency difference of the two waves with the same amplitude, which ...
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59 views

Effect of motion of medium on frequency

Will the frequency observed by a stationary observer will remain same if only the medium between the source and observer is moving?(ie. both source and observer are at rest and wind is blowing from ...
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Amount sound is reduced when emitted from behind observer [closed]

If an object is in front of an observer and it emits sound, the observer hears the sound at 100%. But if the observer facing the opposite direction of the object emitting sound, how much less sound ...
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Can I measure the mode shape frequency of a metal frame with a sound meter

If I 'ping' a metal frame it will resonate in many different mode shapes with different frequencies. I can see those shapes by doing a modal FEA analysis. When I use a sound meter to measure the ...
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17 views

How to convert from overtone to harmonics and vice versa?

I was given this question: If the pipe length in a tube is 1.9 m, at the air temperature inside the tube is 28 °C, determine the fundamental frequency of the note played, fourth harmonic and the ...
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59 views

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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36 views

Subtracting Audio from a Song with Multiple Forms

This question may start oozing into the realm of copyright infringement, but let's discuss the theory first and foremost. I have a song with vocal and orchestral accompaniment from a well-known movie ...
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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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Speed of Sound in matter

So basically when it comes to the speed of sound, it is said that speed of sound in media is based on two main factors - 1)elasticity and 2)density from the formula V= $\sqrt{E/\rho }$ where E is ...
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63 views

What does a sound of infinite Hz sound like?

Say an airplane flies at Mach 1. The doppler effect causes the front of the sound emitted by the plane to reach infinite frequency: $f = \left ( \frac {343+0}{343-343} \right ) f_0 = ∞$ If the ...
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How to create planar acoustic waves?

The only way I can think of for creating planar acoustic waves is using a 2D phased array of transmitters, but even then the planar wave is not so planar (depends on the interference pattern, which ...
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How to measure dB in terms of factor?

We know that, 3 dB means factor of 2. 10 dB means factor of 10. By using this information, I want to calculate 1 dB to 10 dB in terms of factor. What could be the approach? Till now, my ...
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Infrasound vs. Ultrasound

Can an ultrasound device be used to cancel out the effects of infrasound waves on humans? This is a discussion question among a science group to which I belong. Thanks for your answers.
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Why does the length of a wind instrument affect it's pitch?

I understand how length of a string on any string instrument affects it's pitch, but I don't understand how a short wind instrument produces a high pitch.
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3answers
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why doesn't pitch or volume change the speed of sound? [closed]

If sound is a propagated by particles hitting each other in a tranverse wave, why doesn't pitch affect the speed of sound? Since frequency is the speed at which the particles hit in a period of time, ...
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107 views

Pressure standing wave nodes at the end of the open side of a tube

I do not understand why standing sound waves can be formed in a one-side or two-side open tube. Consider a one-side open tube. In particular how does the reflection of the wave at the open end occur? ...
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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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Do clouds reflect ambient noise?

On days with a full blanket of low-hanging clouds overhead it seems I can hear more trains/traffic in the distance. Do clouds actually reflect ambient noise or is this some trick of the imagination?
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Intensity of the acoustic waves coming out of the speakers at the very beginnig of their “journey”

According to the formula, the intensity of acoustic waves at any given point is: $$I(R) = \frac{P}{4\pi(R)^2}$$ where P is the power of the source and R is the radius of the force (Assuming that the ...
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How to phrase the question of measuring the frequency of a complex sound?

I was hoping I could crowd source some understanding. Im interested in understanding the measuring of sound pitch. From what I've been able to gather thus far- sounds are waves of air pressure and ...
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54 views

Energy in a sound wave possible error?

In a certain text discussing longitudinal waves it stated that for a sound wave, both the kinetic energy and potential energy are maximum at the same time. I always thought that the potential energy ...
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Measured organ pipe eigenfrequency does not match the theory

There are many well-known homework assignments to find eigenfrequencies of an open organ pipe leading to the solution for the fundamental frequency of such a pipe: $$f_0 = \frac{c_0}{\lambda_0} = ...
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How to find distance from sound source given sound level

I've done a similar problem to this before, only it included speakers and the problem specifically stated that the sound spread out spherically. So I'm not sure if I'm always supposed to assume that ...
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Equipment to measure the distance to a sound [closed]

Do you know if there is some sort of equipment that can measure the distance to a sound? What practical application can such an equipment have? The reason I'm asking is because I just got an idea of ...
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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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19 views

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 ...
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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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1answer
44 views

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 $$ ...
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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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4answers
57 views

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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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, ...