# 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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### Does the speed of sound wave change when the source velocity change?

The speed of sound in air is about $740$ miles per hour. Suppose that a police car is sounding its siren and is driving towards you at $60$ miles per hour. At what speed is the sound of the siren ...
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### Transduction coefficient of an electromechanical system

I have been recently doing a physics experiment which requires me to determine the transduction coefficient of a speaker system, undergoing electromechanical resonance, in an AC circuit. The quantity ...
0 votes
1 answer
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### Long wavelength limit of sound wave

I often heard the statement that the deformation of the system corresponding to a sound wave in the limit $k\rightarrow 0$ must go over into a displacement of the system as a whole. I don't understand ...
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### Can sound waves deform (curl brake) like water waves?

As far as I understand, both water waves and sound waves are mechanical waves, in the sense that both are created by the relative movement of particles in a certain medium. Sound is propagation of ...
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### Particle Velocity vs. Wave Velocity of a Longitudinal Wave

I am having some trouble disentangling the concept of particle and wave velocity for acoustic waves. Because the waves are propagating along the same plane as particle oscillations, I would (wrongly) ...
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### Confusion Regarding the General Formulation of Specific Acoustic Impedance

I am having trouble understanding the general formulation of specific acoustic impedance: $$Z = \frac{P}{s}$$ This equation is telling me that if I, through some means, increase the pressure of an ...
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1 answer
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### Difference between Optical Wave Equation and Acoustics Wave Equation

I used to work on fast algorithms for solving acoustical wave equation, e.g., as explained in https://en.wikipedia.org/wiki/Wave_equation. Now I am working in a semiconductor company, and we study ...
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1 vote
2 answers
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### Why does density change the resonant frequency of a wineglass?

I’ve been looking at various sources, and they all say that density effects the energy transfer from oscillations of the wineglass (in other words, the heavier and denser the liquid, the more energy ...
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### Does the material of the horn affect the matching of the acoustic impedance of the horn with that of the air?

I am trying to design a directional trumpet, but I think the most important issue is the matching problem with the acoustic impedance of air. Does the impedance of a horn relate only to the dimensions ...
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### Why is the mouth of the horn for ultrasonic air transducer narrower than the throat?

Generally, the mouth of an acoustic horn is wider than the throat. However, most of the horns for ultrasonic air transducers are reversed. what is this aimed at?
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8 answers
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### Does a tower bell ringing prevent thunderstorms?

Introduction This is the beginning of an apparently physics-unrelated question, which involves 1700-1800 Italian law, atmospheric processes, sound waves propagating through fluid and clouds, and ...
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### Which is superior, piezoelectric ultrasonic transducer or compression driver unit?

I think the starting point is to raise the sound pressure level of the primary radiator in transmitting the audible sound as far as possible. In order to create the maximum sound pressure in ...
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### How many dB can the sound pressure level be amplified by installing a horn on the compression driver?

I bought a 113dB compression driver with good sensitivity, but it still does not reach the required level. I am trying to increase the sound pressure level to the maximum using the horn, but I want to ...
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2 votes
1 answer
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### Symmetry of hearing and speaking

Can two people be situated such that person A can clearly hear person B, but not vice-versa? Assume that both of them are free to turn any direction in $S^2$ from their position, and that they are ...
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### Difference Between a Time-Domain and a Simulation Domain Acoustic Pressure Simulation

I would appreciate it if someone would be able to clarify my doubts. I'm currently working on acoustic simulations in COMSOL and is currently confused on the information provided by the simulations ...
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1 answer
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### Waves and oscillation [duplicate]

Maxima and and minima of sound wave at given time represents air density (maxima represents compression) similarly. How does these curved lines over the water surface represent variation of air ...
-1 votes
2 answers
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### How do I calculate the boundary between the near field and the far field of plane array loudspeaker?

I am consistently obsessed with transmitting as much audible sound as possible. A lot of progress has been made with your help. What I would like to ask is to increase the frequency moderately in ...
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### How do you determine the dimensions of the horn to maximally sharpen the beam of the sound source (piezoelectric vibrator)? [closed]

We are going to use a horn to maximize the sound created by a vibrating diaphragm, as in a horn loudspeaker. When the voltage applied to the vibrating diaphragm is kept constant, is there a limit to ...
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0 votes
1 answer
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### What is the reason that the vibrating body gradually acquires the frequency of the external periodic force in forced vibration?

When an external periodic force is applied on a vibrating body the body no longer vibrates with its own natural frequency but it gradually acquires the frequency of the applied periodic force. I don'...
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1 answer
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### How do I calculate the attenuation per distance of a sound wave with sharp directivity?

In general, I think that the inverse square law according to distance in acoustics is due to the field created by the point source. How do you calculate the sound pressure level according to the ...
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### Sound, additive principle or not? How to prove?

If we have $N$ sound sources with $L_1, L_2,...$ with intensities $I_1, I_2,...$. How to prove that $I_{total}= I_1 + I_2 + ...$ but $L_{total}$ is NOT $L_1 + L_2 + ...$
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### What would be the effect of wind in the wavefronts coming from a isotropic source?

Consider a situation where a isotropic point source is kept on ground and its emanating sound waves which would be radial outwards . Consider now wind starts blowing towards left side , what would be ...
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### Step-by-step resolution of the homogeneous $2^{nd}$ order differential equation of the wave [closed]

I am trying to solve this homogeneous $2^{nd}$ order differential equation of the wave : $$\frac{\partial^2{\sigma}}{\partial x^2}-\frac{1}{v^2}\frac{\partial^2{\sigma}}{\partial t^2}=0$$ I am trying ...
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4 answers
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### Question about the Wave equation

I have a question. I was looking for the Wave equation (first Eq. of this wikipedia page). I saw for the first time a version of this equation during an Acoustic course, where we obtained it for the ...
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1 answer
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### Inelastic ball bounce (sound vs. heat)

Today in my son's physics class, his teacher asked why a superball does not bounce as high as the point from which it is dropped. At dinner when my son repeated this question, I answered that a small ...
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1 answer
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### Can sound waves affect the regularity of crystal positions in stone as it cools?

I've long wondered if it would be possible to hear the speech of ancient peoples by scanning sequential imperfections in crystal formations of fire-side stones as they cooled down and solidified (for ...
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1 answer
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### Experimental Values for Amplitude $\delta^*$ of Particle Displacement in Acoustic Fields?

I've been searching but have been unable to find any experimental values for the amplitude $\delta^*$ of the particle displacement from equilibrium that particles in a medium such as air will undergo ...
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### Does self-demodulation occur in air when ultrasonic waves are modulated and transmitted with audible sound?

I have heard that there is a technology that modulates ultrasonic waves into audible sound through multiple paths and sends them out. The reason for using this technology to send the voice as much as ...
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### Reflection coefficient for acoustic waves for normal incidence

Suppose I have two mediums separated by a boundary at $x=0$. A wave, travelling from left to right, would get partly reflected and partly transmitted. Left of the medium, I can write the total ...
6 votes
1 answer
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### Does gravity slow down sound (does sound travel faster downwards than upwards)?

I have read this question: So assuming the heavier planet has the same atmosphere as Earth, and that we can treat the atmosphere as an ideal gas, the speed of sound on the heavier planet would be the ...
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1 answer
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### What is the maximum distance that music is transmitted through the air?

I would like to hear your advice on which method to use to transmit music or speech in a frequency band that is sensitive to the human ear up to 3km. Everyone knows that the higher the frequency, the ...
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