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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How to explain the difference of attenuation of different pitch of sound by kinetic molecular energy?

How to explain the difference of attenuation of different pitch of sound by kinetic molecular energy ? I know that «sound of low frequencies travel farther in air than sound of high frequencies». ...
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Why does the speed of sound decrease at high altitudes although the air density decreases?

I understand that the speed of sound is inversely proportional to the density of the medium as shown here and as answered for this question. The problem now is that the speed of sound in air actually ...
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Is it possible to block sound? [duplicate]

Is it possible to block/eliminate particular noise sounds with artificially generated sound waves or any other ways?
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64 views

The shape of a crest and a trough on wave

what is the significance of the shape of a crest. For example, in the figure below, we can see that one graph of sound pressure shows sharp crests while the other shows smooth crests. How does this ...
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Why do male and female voice pronunciation is same in spite of different voice frequency?

I mean male and female voices are made up of different frequency range but when we produce same word suppose 'cake', we understand it as same.
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Sound frequencies travel at the same speed?

as the diagram shows sound frequencies travel at the same speed or each frequency has a given speed ?
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What happens to a wave when the tube changes in diameter

everywhere they only show the single diameter tube, but they don't explain what happens to the wave when the tube changes its diameter Is someone kind enough to graph me how the wave changes when ...
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25 views

the mechanism of sound generation of plunging jet

can anybody give me an explanation about what is the acoustic source for a plunging jet, like tap flow enter into a basin? is there any exiting theory like Lighthill theory in aero-acoustic to explain ...
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26 views

Pitch of balloon popping

How does the pitch of the sound of a balloon's pop change based on the pressure inside the balloon? Or does only the loudness of the sound differ? I assume the sound doesn't really have a definite ...
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Pressure variation in a sound wave

My teacher told me that pressure variation is maximum at mean position in a sound wave. Though by proof of pressure wave and displacement wave, I am convinced but in understanding the physical ...
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1answer
52 views

Why is the kettle loud, but the induction hob is quiet

The question: "Why is a kettle loud?" has been asked and answered many times, including on here: Why is boiling water loud, then quiet? What is the reason for this pattern of noise in electric ...
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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 ...
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How are standing wave patterns created in tubes?

I get how standing wave patterns are created in strings: At a certain resonance/natural frequency of the string, a standing wave is created, increasing the amplitude of the sound, and standing waves ...
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What is the difference between a Surface Acoustic Wave (SAW) (Rayleigh Wave) and a Leaky SAW?

I have come across leaky SAWs and I'm not sure what the difference is, and why some substrate cuts are listed as leaky SAW design. Trying to search for diagrams so I could see what the differences ...
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Is there any relationship between a solid material's natural frequency and the speed of sound through the material?

It seems like there should be a mathematical relationship between the two - is there?
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89 views

Volume of a speaker needed to boil an egg [closed]

I have a fun question to ask that me and my friends couldn't figure out. If I was to boil an egg using a speaker, how loud would that speaker need to be? (Yep, this is clearly what keeps us physicists ...
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Young's double-slit in Sound waves [closed]

I am going my physics extended essay and I am stuck in explaining my hypothesis. So I am doing an experiment where I have 2 sound sources emitting specific frequencies and I am trying to find fringe (...
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2answers
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What happens if a traveling sound wave encounters vacuum?

Suppose a sound wave is emitted by an object in a medium like a gas so it travels in some direction. If the wave meets a rigid object, for example a wall, it reflects back as one should expect; and if ...
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1answer
59 views

Do noise-cancelling headphones make a lot of unheard noise?

The way noise cancelling headphones work is by listening to sound, and created the inverted sound to 'cancel it out'. Doesn't this mean that the headphones create double the amount of noise, but our ...
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How does sound change high in atmosphere? [duplicate]

There is no sound in space because there are not enough particles to transmit the pressure wave. But what about really high in the atmosphere where there is just a little air? Would sound move faster, ...
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How can I calculate Helmholtz chamber dimensions?

I'd like to do the calculations on this page manually Cavity Resonant Frequency as I'm entering in values and the results are outside of what I expect, so I'm hoping to learn the manual way of ...
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Can someone please explain the difference between sound frequency and, say, beats per second?

I'm sure this is a monumentally stupid question buy I'm just stumped. I'm not sure how sound frequency is different than beats per sec from a physics perspective. Humans can hear down to 20HZ which ...
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Why is “a very silent room” louder than “leaf noise” / “breathing noise”?

I recently was at night in my bed room and used the Schallmessung Android App (on a Samsung S7). It showed 20 dB while laying on some furniture. I could not hear anything; to me, the room was ...
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Physical meaning of the convection term in the momentum equation of acoustic wave

In deriving the acoustic wave equation, the momentum equation is used. $$\frac{\partial \mathbf{u}}{\partial t}+ (\mathbf{u}\nabla)\mathbf{u}=-\frac{1}{\rho} \nabla p$$ Intuitively, the convection ...
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On a planet with winds faster than sound, what would it sound like?

I'm watching a Youtube video of the strangest planets and some of them have atmospheres/winds that constantly go at like 20x the speed of sound, ex: HD 189733-b .On earth, fast winds is actually ...
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How to solve this problem involving the “longest interval”?

The problem is shown as follows: If one wants to make a digital record of sound such that no audible information is lost, what is the longest interval, $\Delta t$, between samples that could be ...
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Sound and thin gas films: does the speed of sound become multi-valued?

The basic formula for the speed of sound in a gas $c=\sqrt{\left(\frac{\partial p}{\partial \rho}\right)_s}$ assumes that it is uniform, and thus that sound waves travel through the gas at one speed. ...
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The validity of some “applications” of the uncertainty principle

Given a $L^2$ function $f$ with $\int_\mathbb{R}xf(x)dx=0$, define its variance to be $\sigma_f^2=\int_{\mathbb R}x^2f(x)dx$. The uncertainty principle states that $\sigma_f\sigma_\hat f\geq 1/4\pi$,...
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Sampling rate required to detect phase shifts of certain resolution

I have a closed-ended pipe, that has is 2-3cm long (the opening is 1cm in diameter). I would like to determine it's length by sending an acoustic sine wave and looking at the phase of the reflected ...
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Determining length of tube from acoustic reflection

I am interested in determining the length of a closed ended tube. I would like to do this using an acoustic signal, like a sine wave. Depending on the length of the tube, I believe the reflected ...
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1answer
103 views

How quiet can a bouncing ball be when it hits the floor?

When non-elastic balls like a putty ball hit the ground they should waste their kinetic energy on heat and sound, much more than elastic balls. However putty balls hit the ground very quietly while ...
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1answer
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Sonority of metals [closed]

Is there any reasonable atomic theory which can provide a rational reason for the existence of sonority in metals? Almost all the non-metals do not exhibit sonority. Can it be correlated to the ...
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1answer
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Why does sound attenuate in air differently in different situations?

Sound attenuates in air, and some frequencies go quieter quicker than others. But it feels like which frequencies get quieter should be consistent. Here's two opposing examples: At a party, there's ...
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What's the difference between shock waves and acoustic waves?

What's the difference between shock waves and acoustic waves? I tried and searched around this subject, but I could not find any relative article about it. Please help me find a proper answer.
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Can two waves interfere head on?

Can two waves (like sound or electromagnetic waves) interfere head on? If yes, and suppose they are out of phase with each other and thus interfere destructively, where does the energy of the waves go?...
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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 ...
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Doppler shift moving parallel to wall [closed]

Suppose you are screaming and running in an area parallel to a wall. What would be the frequency you hear considering that you are getting away from the part you've passed and getting close the parts ...
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What is Rectangular Simple Harmonic Motion (SHM)?

While studying Simple Harmonic Motion and Lissajous figure, I found a term called Rectangular SHM. But what is it actually? Is it something like square wave? What is the difference between Linear and ...
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Why don't humans perceive sound waves as twice the frequency they are?

I was reading about how at how acoustic beats work. If we combine two waves with frequencies $f_1$ and $f_2$ and unit amplitude, their combination is $$ \begin{align} A &= \cos\left(2\pi f_1x\...
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Why do jet engines sound louder on the ground than inside the aircraft?

Everyone is familiar with the whirring sound of jet engines when seeing an aircraft taking off from a nearby airport. It is distinctly very loud on the ground and one can hear it even when the ...
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1D multipole Green's functions for the wave equation

What are the Green's functions for longitudinal multipole sources for the homogeneous scalar wave equation?
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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 ...
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Possible to separate audio from separate sources into separate audio streams using multiple microphones? [closed]

I want to be able to separate audio from separate sources into separate audio files. I know that audio takes time to travel, so there could be differences in recording time for the same "woohoo" sound....
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Sound wave and Principle of relativity

Principle of Relativity: "An experimenter doing an experiment in an inertial frame of reference can never measure the velocity of its own frame of reference. OR a law of physics is never expressed ...
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What happens as wavelengths of sound waves approach tens of micrometers?

I was having an online conversation about Dungeons and Dragons, and my acquaintance abbreviated "Barbarian Level 17" as Bb17. I took the opportunity to make a joke about how that is similar to musical ...
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Definition of medium?

Why do we define vacuum as space devoid of matter? we say that electromagnetic waves can travel through vacuum while longitudinal waves can't. We also say that the velocity of sound waves (a ...
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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 ...
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Why do earphones cause pitch shift in external sounds?

I was walking down the street with my earphones in, nothing playing, and I noticed a car alarm blaring from behind me. I took my earphones out, and the car alarm shifted slightly in frequency! I ...
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Is it true that if one stood on Westminster Bridge with a radio, one would hear the chimes of Big Ben via the radio sooner than in the real world?

I was reading this review of Damon Krukowski’s Ways of Hearing in The Spectator when I stumbled across this claim: “And before the renovation of Big Ben began, if you stood on Westminster Bridge ...
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How to calculate the position and number of holes to put into a woodwind so it is able to play a certain set of pitches?

I'm in the process of building a bamboo flute, or perhaps a "saxophone" of sorts. I don't know how to calculate and find out the possible finger hole schemes to achieve the range I'm looking for. I ...