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.

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An equation that explains the relationship between the sound strength and medium pressure

I am doing an experiment that explores the correlation between sound strength and air pressure. Experimentally I got that by increasing the air pressure, the sound strength increases with it. My ...
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2 answers
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Does the wavelength of a sound change from one medium to another?

In my book, it is written that: v = fλ in a given medium under conditions of fixed temperature and humidity. It is also written that: one of the more important properties of sound is that its speed ...
2 votes
2 answers
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In what respect does the wave pattern of a noise and music differ?

Does the wave pattern of musical sounds contain only harmonics (other than the fundamental frequency) while noise contains random overtones (that are not harmonics)?
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What is ratio of the intensities of these two equally loud sources? [closed]

A 50 Hz source is perceived to be equally loud as a 1 kHz source at 20 dB when its intensity level is 50 dB higher than the 1 kHz source. What is the ratio of the intensities of these two equally loud ...
2 votes
1 answer
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Do lower frequency sound waves penetrate through materials better than high frequency waves

I was doing a physics experiment today where we played different frequencies at the same volume and a sound recorder at the other end with a sheet of cardboard in the middle. We found that the higher ...
1 vote
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How will be the effect of temperature and density on a sound wave at the same medium?

Let think about a sound wave travelling a medium.There is a theory that if the temperature is increased,the speed of sound wave will be also increased as the molecules have more energy and it can ...
2 votes
1 answer
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Does energy conservation law conflict with Active Noise Cancellation

Assume the picture below: From inlet port In1 and In2 we can have electromagnetic or acoustic energy entrace single sine wave with same amplitude and frequency. Assume we have aligned the waves to ...
2 votes
2 answers
60 views

Is there any kind of material medium through which sound does not travel at all?

In my book it is written, the conditions necessary for the propagation of sound are: A vibrating source for the production of sound. A material medium for the sound to travel through. The material ...
1 vote
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Particle displacement from pressure [closed]

Is this correct? I'm looking for other sources of the result. If pressure at a point is sinusoidal $$ p=p_0 sin(\omega t) $$ then particle displacement is $$ \boldsymbol{s} = {1 \over {\omega^2 \rho}} ...
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Can we use Resonance to destroy the ear drum? [closed]

I will play a sound whose frequency is a multiple of the natural frequency of ear drum. So that, the ear drum will be in resonance and vibrates violently and tear apart eventually. Is this even ...
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4 answers
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The frequency of a sound wave in air is 128 hz . What will be it's frequency in water? [closed]

This question could be solved in two ways . But I want to know which is the correct way. It could be be solved by taking the speed of sound which will result in having a wavelength of that sound wave. ...
1 vote
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Recording Analog Data in Optical Disc Using Laser Beam Mechanism [closed]

Is it possible to storing/writing any Analog Audio Signal (i.e. Vinyl Record & etc) into a little bigger and thicker Optical Disc as compared to the other conventional Compact Disc while using the ...
1 vote
2 answers
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Relativistic speed of sound in an inhomogeneous medium

What is the expression for the speed of sound in a medium if the relativistic effects are important when the sound travels there? In the non-relativistic limit the sound speed is $$v = \sqrt{\left(\...
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1 answer
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Why is an ultrasonic transducer able to send energy into a tank without an opposing surface?

The diagram shows an ultrasonic transducer stuck to the bottom of an ultrasonic cleaning tank full of water/detergent. It's not supported at the opposing end - just hanging off the bottom of the tank. ...
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1 answer
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Source term and potential term in wave equation

I have often seen the wave equation as: $\Box \psi(x_1,x_2,x_3) + V(x_1,x_2,x_3)\psi(x_1,x_2,x_3) = S$; where $V$ represents the potential term ans $S$ represents the source term. I want to know that ...
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Speed of sound and density [duplicate]

The speed of sound in a medium is inversely proportional to the density of the medium. Why?
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Signal Processing – Discrete Fourier Transform and Incomplete Fourier Series

I'm working on a paper where I'm collecting sound pressure data from a chord's wave and trying to create a frequency spectrum to find the individual frequencies that make up the chord. However, I can'...
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1 answer
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Relation between acoustical parameters Definition and Clarity [closed]

In room acoustics, clarity ($C_{50}$) is defined as $$ C_{50} = 10*\log_{10}{\frac{\int_0^{50ms}p² (t)dt}{\int_{50}^{\infty}p² (t)dt}} $$ and definition ($D_{50}$) is $$ D_{50} = \frac{\int_0^{50ms}p² ...
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1 answer
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Decibels, acoustic intensity and sound perception

I know the formula: $I[dB] = log_{10}\left(\frac{I}{I_0}\right)$ with $I$ being the acoustic intensity in $[W/m^2]$ and $I_0 = 10^{-12} [W/m^2]$ being the human threshold of hearing. Also, I am told ...
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How to understand power propagation speed? [duplicate]

When reading papers, I am confused with power propagation speed of acoustic wave in fluid. The problem is given below. For a plane, acoustic wave with pressure $p_i(x,y,t)=Ae^{j(\omega t-kx\sin\theta+...
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1 answer
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Optimization of using a speaker membrane as a propulsion unit - best frequency and shape of the excitation curve

with optimized frequency and excitation curve pattern, a speaker membrane vibrates with a higher speed away from the speaker (representing frequency 1) and with a lower speed back to the speaker (...
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2 answers
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Is sound registered as weight by a scale?

Okay, weird question. I know a sound wave is energy and energy has a mass equivalent, but this question is about weight not mass, or at least as it is read by a scale. Assume that a loud sound is ...
2 votes
4 answers
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If frequency of a sound wave increases, why does the speed of sound remain the same? [duplicate]

Could someone explain why speed of sound doesn't change when frequency is increased? My thinking is, if frequency increases then the period will decrease, thus air molecules will be oscillating faster....
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How does the speed of sound relate to the phase velocity and the group velocity? [closed]

Let us suppose we have a 1D atomic structure of masses $m$ attached with spring $\kappa$. Now given the following dispersion relation $$ \omega(k) = 2\sqrt{\frac{\kappa}{m}}\Big|\sin{\left(\frac{ka}{2}...
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What is the frequency spectrum of an "instantaneous" excitation force?

Suppose you have a brass rod and it gets excited by an (almost) instantaneous force, for example by a hammer hit. Now, this force is acted upon the rod for a specific amount of time, let's call it Δt. ...
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Eliminating sound vibrations by using destructive interference for sound waves

Can you eliminate sound vibration (when either it is audible sound, ultrasound or infrasound) by creating a destructive interference, but when both sources are in opposite sides? Say, you have one ...
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Source for Ultrasonic Nondestructive Testing (US NDT)

I need a good source to understand Ultrasonic Nondestructive Testing (US NDT) I can't seem to find a lot of explanation for the topic in English online although it is very important for any engineer/...
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1 answer
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How to reconcile the explanations for why sound travel faster in solid than air? [closed]

In high school (and almost all the youtube videos), we are often taught that sound travels faster in solid than air because solids are generally denser; this allows the air particles to more readily ...
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Is there a 'better' tuning frequency than 440 Hz? [closed]

My apologize if this question is a bit broad or open ended but I'm asking here rather than a music forum for two reasons: I'm trying to gain a better understanding of the physics of sound and ...
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Resonance and differential equation

I've read that resonance can be modelled by the differential equation: $$\ddot{x}+\omega^2x=f\cos(\omega_\text{d} t), \quad x(0)=\dot{x}(0)=0$$ However, it's mainly explained in the context of a mass-...
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Acoustic Levitation Calculations

I have recently started studying acoustic levitation and I would like to lift an object that is about 2.5 pounds. Surface area is about 5in x 5in. I am not very knowledgeable on the subject and I have ...
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2 answers
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How Do Soundwaves Move and Influence Specific Particles or Gases? Natural Resonant Frequencies?

So I was browsing about natural resonant frequencies and how they work, and I stumbled upon this article: https://www.euronews.com/2022/01/21/polish-town-tests-anti-smog-sound-cannon-to-tackle-...
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Resonance Frequency in a Tube

I am trying to design a physical experiment to find the acoustic resonance frequencies of a plastic, cylinder pipe, to draw an analogy to the workings of musical instruments such as a flute. However, ...
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Unstable acoustic mode

For a stirling thermoacoustic engine that works with a simple stack inside a test tube (with temperature gradient), it is said the frequency at steady state is that of the most unstable acoustic mode -...
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Confusion over textbook formulae for directional characteristics of sound sources

I'm currently reading Olson's Elements of Acoustical Engineering, in which formulae are given for the directional characteristics of various arrays of sound sources, all of which are stated in terms ...
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1 answer
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Intuitive understanding of the unit $kg/s^3$ — the unit of sound volume

I know that decibels are used to measure volume of sound, and they are basically a logarithm of $kg/s^3$. The best explanation that I have for the unit of $kg/s^3$ is that it is an alternate way of ...
1 vote
1 answer
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Optimal Way for Transmission of Sound from Air to Water [closed]

Is there a best way to transmit sound from air to water? The route of the sound doesn't have to be air -> water directly (i.e. it can be air -> [some sort of medium] -> water). I am trying to ...
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1 answer
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Why does the amplitude decrease due to friction in forced vibrations?

Basically, in forced vibrations the frequency of the external force is acquired by the body when both the natural frequency and external frequency is different (won't go into that too because I'll get ...
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2 votes
2 answers
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Is supersonic movement possible in incompressible media? [duplicate]

When reaching the speed of sound in air a shock-wave starts building up in front of the object moving at sonic speeds where the air is compressed. But what happens, if the medium is not (or almost not)...
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Why antinodes must be present at the free ends of an open organ? (Neglecting end correction)

Why cant a node or less than an antinode be present at the free ends of an open organ pipe. What's the logical reason behind an antinode existing at the open organ pipe? When I asked my teacher this ...
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What will be the pressure function of sound wave [duplicate]

Given a displacement function $s=A\sin(\omega t-kx)$, I read from several books and found that some say pressure leads displacement and give the pressure function as $p=p_0\sin\left(\omega t-kx+\frac{\...
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How much frequency is needed to make a tennis ball levitate, using only sound? [closed]

I am planning to make a device that will catch a tennis ball using sound waves to slow down its motion, and make it levitate. But how strong should the sound waves be? Please tell me if there are ...
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1 answer
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Thermoacoustic mechanism for a thermoacoustic engine

How exactly does a thermoacoustic engine work? (I don't mean the engineering part) I understand the part on the Brayton cycle occurring and all, but how might we measure the numerical efficiency for ...
23 votes
6 answers
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What's the difference between a microphone and a barometer?

A barometer is a device that measures air pressure A microphone is a device that detects sound waves. Sound waves which travel through air. Pressure of a gas is caused by the motion of the gas. So, a ...
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Sending sound waves down a pipe to measure water depth -- Destructive interference?

I will be attempting to use sonar in order to measure the height of a groundwater well. In theory, I will have a device emitting sound waves down a tube made of plastic/metal/rubber. Do I have to ...
1 vote
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I have a doubt regarding the reflection coefficient result for 'reflection and transmission of waves at a boundary'

So I found out that result for reflection coefficient is given different in different textbooks and websites. This really confused me as with one kind of result everything satisfies with free end &...
15 votes
3 answers
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How does the string of an acoustic guitar transfer energy to the guitar's body?

I've learned through the answer to this post that the purpose of the soundboard of an acoustic guitar is to match the impedance of air, facilitating the energy transfer from the strings to the sound ...
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1 answer
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Problem in understanding wave equation in a gas column

In my textbook, the author derives the displacement wave equation in a gas within a cylindrical pipe (when the deformation of the gas is small): $$\frac{\partial^2\xi}{\partial t^2} = \frac{B}{\rho_0} ...
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HOW are harmonics generated in longitudinal waves on the particle level?

I have been looking through the physics.se and all over the internet for weeks now honestly, and I still don't understand how harmonics are formatted on the particle level. Yes, I know that only ...
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Not so much a question as it is an added facet to an earlier question about sound propulsion [closed]

Ok so sound doesn't travel in space... But what about frequencies... And what about propulsion through Hz? Simply amplify one frequency at one speed then the next one a little faster but at a smaller ...

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