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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Why does light not produce sound?

We have heard about the definition of a wave - disturbance in the matter or something. But can we think that light is a wave and so does it have vibrations (oscillations). Does it produce sound then? ...
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What's the speed of force? [duplicate]

Brain storm: Suppose we have a perfect lever, which has 0 quality, and perfect rigidity. It is long enough that can reach Proxima Centauri from the earth. Someone push one side of lever from Proxima ...
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Beat frequency in instruments

I was recently learning about beat frequencies, that is, when sound waves slightly out of phase overlap and result in a beat. I thought that this sounded similar to the vibrato in stringed instruments....
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Are the speed of sound and water ripples' speed the same?

When a droplet of water hits the surface of a lake it produces ripples that travel outward. My conception is that it travels at the speed of sound in water (since sound are nothing less that ...
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Why can't I hear audio from two different speakers in two different rooms, at the same time, if I am in one of the rooms?

There is a speaker in the living room, and close by in the kitchen there is a ceiling speaker playing audio from the same source. Why can I only hear audio from the kitchen if I am in the kitchen? ...
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How are people able to procure sounds from electromagnetic waves?

I have found out about this video: https://www.youtube.com/watch?v=lO5ehpdZ5Po, and also this one: https://www.youtube.com/watch?v=Cga3DfaLc7A. The first one is about a device called the Elektrosluch (...
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Physics experiment with sound [duplicate]

I am doing an experiment for a school project which consists of blowing into 6 different bottles to create different notes/harmonics. Each bottle is filled with different volumes of water to create a ...
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2answers
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During sympathetic resonance in a piano, are new frequencies generated?

Sympathetic resonance in a piano is the phenomenon of one string being excited, transmitting its sound to other strings that will then start vibrating if they have common frequencies. For example C2 ...
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Why loudness is dependent on number of molecules?

Loudness is dependent on amplitud,e which in turn is dependent on number of molecules. The more the number, more the amplitude. But isn't amplitude just a measure of how displaced can the particle be ...
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Ultrasonic wave - connection wave speed to amplitude?

An ultrasonic wave is sent through a dispersive medium. That means the waves move at different frequencies with different phase velocities. If this were measured in the frequency spectrum, would the ...
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Metal - dispersive media?

Can metal alloys be regarded as "dispersive media" if they are excited with ultrasonic waves?
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How acoustic shock waves create and propagate in fluid?

I would like to understand how a shock wave is formed starting from the comservation equations. I know how to obtain a the wave equation with a perturbative approach (i.e assuming very small ...
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If 30dB at 200 meters away, how much at origin? [closed]

I want to organize an event in a public area, and I'm not sure how loud we can get. If the limit is 30 dB as measured at 200m away from the origin of the sound, what is the limit from its origin, in ...
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Why do we hear beats?

I've learnt quite recently that to hear beats the sources must emit sound in almost near frequencies Here is a scenario I have a two tunning forks and together the produce a beats of frequency 2hz But ...
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Geometrical acoustics derivation

In acoustics for non-uniform media (speed of sound is $c(\mathbf{r}, t)$, dependent on space and time), I want to solve $\frac{\partial^2\phi}{\partial t^2}-\nabla^2(c^2\phi)=0$, where $\phi$ is the ...
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Why do string instruments need hollow bodies?

My textbook states, 'The sound box has a large area, it sets a large volume of air into vibration, the frequency of which is same as that of the string. So due to resonance a loud sound is produced.' ...
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Why don't we burn ourselves when we speak?

In this post we learn that sound transfers a lot more energy than heat across the medium, so why don't we burn ourselves when we speak by generating sound? Does sound reflect more easily than heat?
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Why does an audio signal sound differently if we randomly flip gradients between each adjacent pair of samples?

Let's assume the samples of our audio signal are always in the interval [-1,+1]. When flipping all the samples (multiplying them by -1), listening to the sound ...
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Can we add bosonic phonon in the Standard Model of Particles?

Nowadays, we describe phonon as “particle” of sound. They have zero spin but are thought to have mass and kinetic energy. Phonons are the smallest units of the vibrational energy that makes up sound ...
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Note cancelation

I was playing an Irish whistle with a worship band. I was playing though a vocal mic and listening with in ear monitors. On a high pitch, the note seemed to disappear. Is this a natural phenomenon or ...
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Are mach cone and vapor cone the same or not?

I have read numerous articles, claiming that Vapor cone IS NOT the mark that aircraft is passing "sound barrier", or, in other words it is not the visualization of Mach wave But I can't ...
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29 views

Electric current and motion of electrons

When a battery provides energy to an electric circuit, the electrons get aligned so as to transfer energy from the negative terminal to the positive terminal. The drift velocity of the electrons in a ...
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Derivation of speed of sound in (diatomic) chain using Newton-Laplace formula

I am familiar with the derivation of the speed of sound done in the style of, for example, this question: Diatomic chain and speed of sound I would like to derive that same result $$ c^2=\frac{2ka^2}{...
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Why do water drops make a louder sound when they land on a bucket , when compared to a solid floor?

I noticed this yesterday in the shower and my physics sense tingled. well im here now !
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Does noise-cancelling cancel out the impact of a loud noise on your hearing?

So what I am trying to ask here is whether noise-cancelling headphones are actually working because the listener hears both, the noise-cancellation acoustic wave as well as the original acoustic wave, ...
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1answer
33 views

Division of intensity of sound

Consider a single sound source $(S)$ producing sound wave of intensity $I$ . It is connected to a detector $(D)$ through two paths with a path difference. My doubt is that will the intensity of ...
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What do “elastic property” and “inertial property” mean in this passage about the speed of sound in elastic media?

I was reading the chapter Sound Waves from my textbook and I came across this line that I am unable to comprehend properly. Here's how it goes - The speed of an mechanical, transverse or longitudinal,...
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Help Solving a Boundary Integral Equation for the Acoustic Analysis of a Quadratic Residue Diffuser-Topped Sound Barrier

it has been a while since I've attempted partial derivatives but I am hoping that someone can help guide me in the right direction so that I can solve a specific equation that attempts to calculate ...
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Wave vector in spherical coordinates

I understand the wave vector for plane waves in Cartesian coordinates. Along the direction of propagation of wave, $$k = \sqrt{k_x^2+k_y^2+k_z^2} = \frac{2\pi}{\lambda}$$ If $(k_x, k_y, k_z) \neq 0$, ...
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I need help with calculating the intensity of ultrasound

A distance meter, see the picture below, uses ultrasound with a frequency of 50 kHz. The ultrasound is generated by a circular piezoelectric transducer (flat surface that vibrates) with a diameter of ...
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Do bats use special relativity when they use echolocation?

I'm trying to find a "classical" thought experiment to form a better intuition for special relativity. Bats are creatures that observe their world via echolocation. Their observations are ...
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Is Wikipedia wrong regarding the Kundt’s tube?

Here is the Wikipedia article on the Kundt’s tube. It says: The powder is caught up in the moving air and settles in little piles or lines at these nodes, because the air is still and quiet there. ...
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Why does Kundt’s tube produce striations?

Why does the Kundt’s tube form these striations? I am looking for the simplest answer possible.
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How does pitch change when sound velocity change?

The hot chocolate effect makes the pitch of sound of hitting a coffee mug lower when you stir the liquid within. The explanation is that you lower the pitch because velocity lowers inside the bubbles ...
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How objects with very low frequency generate sound?

From what I understand if an object vibrates with a frequency between 20-20k Hz audible sound is generated (for humans), I have also observed this with speakers. However, many times I get very ...
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Changing Voltage

Today I noticed this happening that while my laptop was connected to the charger and there were small voltage fluctuations in my home, I could hear some clear sounds in my earphones (while they were ...
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Why is the formula for the speed of sound in solids different from that in liquids and gases?

We know that sound waves are longitudinal waves and that the propagation of longitudinal waves depends on the bulk modulus $B$ (volumetric elasticity). Why, then, does the speed of sound in a solid ...
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How do we know sound pressure squared is proportional to the power in the sound wave?

I am trying to find the equation that explains why we can say the pressure exerted by a wave (squared) is proportional to the power. I see this claim made a lot but I can't tell where it comes from.
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Measuring the harmonics of a vibrating string

I have a string which is vibrating at a fixed frequency, say 1 kHz. I know it is vibrating in a purely first harmonic mode because of the (sinusoidal) drive function I am using. With a microphone I ...
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27 views

Can a Mach number be defined for a hot gas fluid element using its own temperature and velocity?

I know that the ratio of an object's speed to the local sound speed is called the Mach number: $$M = \frac{v}{c_s}$$ where $$c_s = \sqrt{\frac{\gamma kT}{\mu m_p}}$$ I have always thought of the Mach ...
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Can the Helmholtz equation be applied for a system with multiple frequencies?

Currently I am working on a problem whereby I need to solve numerically the propagation of waves in water. My past experiences with this problem is to use the Helmholtz equation to model the standing ...
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A charged particle in a mass spectrometer travels approximately the speed of sound. Do charged particles share similar properties with sound waves?

I've calculated the speed of a charged particle in a mass spectrometer through the Bernoulli equation to be around the speed of sound. I've also seen marketing videos from mass spectrometer vendors ...
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Can sound be used for propulsion?

I'm no physicist so this might seem absurd. I Remember watching a cartoon as a kid where the character uses a powerful speaker to propel his cart and I was wondering if this was actually possible. ...
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329 views

Why is a kalimba note anharmonic?

I play a kalimba, and have also recently written a toy program that helps me tune it using a "naively applied FFT" without any sophisticated DSP. The Nyquist frequency is 24 kHz. The kalimba ...
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Why the person at back on a two wheeler feels hard to listen to sound of the person riding

Situation Today while I was riding a two wheeler(activa) and was talking simultaneously my sister behind me complaint that she wasn't able to hear anything I was saying but I dont get it when we are ...
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Do different kind of waves in a medium interact with each other?

Say for example, air and sound can both propagate to air. Now, suppose we have a sound and light wave travelling close by, how would the two waves interact with each other? Suppose I made a very large ...
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How can we discern so many different simultaneous sounds, when we can only hear one frequency at a time?

As I understand it, the eardrum works like any other kind of speaker in that it has a diaphragm which vibrates to encode incoming motion into something the inner ear translate to sound. It's just a ...
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How does a gramophone work?

A gramophone needle moves on a groove with a radius. How do you relate the length of the groove and the speed of the rotating gramophone plate with the frequency of the sound it produces?
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How does a deadcat work?

This is a deadcat. It's a fluffy cover you put on top of a microphone to prevent wind noise on the recording. Lavalier and head-mounted microphones often use pieces of foam over the mic for the same ...
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Do atoms always move in phase within the unit cell for acoustic mode phonons?

In my condensed matter book it says 'For the acoustic mode, all atoms in the unit cell move in-phase with each otehr (at $k=0$) whereas for optical modes they move out of pahse with each other (at $k=...

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