# Tagged Questions

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### Resonant Frequency & Opera Singers [closed]

Would it be possible under math of strings to note the frequency of each string vibrations? And in doing so, in hand with using the technique opera singers use to shatter glass with their voice, would ...
44 views

### Standing sound wave in a wind instrument

So I've had this question bugging me ever since I saw sound at physics class: How is it possible to match the resonance frequency of a column of air in an organ pipe and form a standing sound wave by ...
50 views

### Compression vs Rarefaction in Sound Waves

I am currently looking into solutions for Sound Classification, and I came across Ludvigsen's methodology (if anyone wishes to refer to it). The problem is that a sample graph of amplitudes in one of ...
60 views

### How do we define a sound source?

How do we define a source of sound? Purely mathematically a sound source is a term $q$ $$\frac{1}{c_0^2}\frac{\partial^2p'}{\partial t^2}- \nabla^2p' = q$$ such that we ...
54 views

### Questions related to resonance/standing-waves and sound

I understand resonance for a simple harmonic oscillator but not for more complex systems like standing waves. How can I be in resonance with the normal mode in an organ pipe? I understand that the ...
19 views

### Compute impulse response of a cavity for sound waves

Given a (closed or not) surface and a point emitting a spherical sound wave, how can I calculate the wave amplitude in any point of space, considering reflections on this surface ? The idea is to ...
41 views

### (air pressure and displacement) Isn't this image wrong?

Isn't this figure wrong? P(x,t) = -B(dy/dx) . If the derivative of air displacement has a maximum, then this is where the pressure is minimum, not maximum as this figure suggests. Could someone ...
31k views

### Can I compute the mass of a coin based on the sound of its fall?

Other day, I bumped my bookshelf and a coin fell down. This gave me an idea. Is it possible to compute the mass of a coin, based on the sound emitted when it falls? I think that there should be a ...
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### can silence happens when 2 sound waves destroy each other [duplicate]

Hi is there any possibility that you located between 2 sound sources and u hear nothing? as we know 2 wave in opposite direction will destroy each other...
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### A strange audio phenomenon, could there be a physical interpretation to it?

http://mathoverflow.net/q/165038/14414 Motivation : Here is a motivation as to why this problem is so important. Let $f(t)$ be an audio signal. We can safely asume it to be bandlimited to 0-20kHz as ...
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### Do eigenvalues in a cylindrical symmetric problem tell us anything about the Fourier spectrum?

During a lecture we were solving the Helmholtz equation for particular boundary conditions, corresponding to different shapes of an oscillating drum, as in the famous Mark Kac's problem ...
4k views

### Why don't two musical instruments sometimes generate destructive interference?

I'm an electrical engineer, and I understand wave propagation, interference patterns, and so on. But I'm missing something basic, so perhaps my understanding isn't as good as I believe. I'll show my ...
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### Standing sound waves phase difference

This is a basic question but I don't fully understand what is going on. When we have a pipe in resonance we get standing waves, where displacement antinodes are at pressure nodes and vise versa. So ...
59 views

### Sound travel problem

Here's an example of my question to make my explanation a bit easier. Say a decent loudspeaker plays a tune at loud volume 100m away from me and another speaker plays the same tune at lot lower ...
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### Does mechanical resonance of an object changes in different surrounding medium?

When comparing mechanical resonance of an object (for example string) in air and in water, does the resonance frequency changes? My guess is that it does change because the surrounding medium will ...
98 views

### Why can't light waves bend? [duplicate]

Assume that you fixed a speaker to an inclined pipe as well the torch. You can hear sound from the other end of the pipe, but can't see the light from other end of the pipe, why?
80 views

### Why doesn't amplitude affect the speed of sound?

I understand why amplitude doesn't affect the speed of the sound AFTER the 'leading compression'. The extra force provided on one stage of the cycle is countered on the other stage. But shouldn't the ...
64 views

### What is sympathetic resonance?

When two tuning forks stand near one another and one is excited, the other rings as well. When high notes are struck on a piano, lower notes are also heard. If I understand correctly, this is called ...
401 views

### How do traveling waves pass through a standing wave node, if the node doesn't move?

I'm having trouble with the explanation that a standing wave in a string is the superposition of traveling waves. The nodes in the diagram above are points where the particles of the string's ...
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### Interference - the shortest way from the point of constructive one to the point of destructive one

So this is a problem from Polish maturity exam. The image shows 2 speakers (G1, G2) and point B. The wavelength of sound coming from both speakers is 0.155 m, and the wave coming from both speakers ...
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### Can the motion of a cracking whip be described as the interference of two waves?

I was watching a whip crack in slow motion and I noticed that the motion of the whip could be described using two different circular descriptions. 1) the user circles the whip around over his head, ...
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### Does sound gets faster when air bubble is supend in water?

Does sound gets faster when air bubble is suspend in water? c = sqrt(K/P) c = speed K = bulk module P = density When air bubbles is homogenized into water the density is lower, so should sound ...
83 views

### Does timbre consist in pitch and volume?

I read that the physical properties of a sound wave correspond to its audible qualities: pitch, volume, and timbre. However, an oscilloscope uses only two-dimensions to accurately depict the physical ...
114 views

### Why are two voices singing the same note louder than one?

Let's say for example: Two people sing the same note (frequency) and volume (amplitude) together. Why is it that the two persons sound louder than they would ...
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### Number of wave modes in a cavity

I'm trying to calculate the number of acoustic modes that can exist in a room in a certain range of frequencies. I thought of using the Rayleigh-Jeans formula for the electromagnetic standing wave ...
161 views

### Are small speakers inherently limited to higher frequencies?

I am hoping to build a subwoofer using multiple smaller speakers (165mm) instead of a single larger speaker (380mm). My theory is that the displaced air volume is what matters, not the individual ...
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### What is sound in terms of acoustic sources?

Sound is nothing more than small amplitude, unsteady pressure perturbations that propagate as a longitudinal wave from a region in space which created it (called the source region) into a quiescent ...
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### What is the longest distance over which echolocation is effective?

Some animals, most notably bats, use echolocation in order to navigate and detect the location and size of objects and prey. This usually takes place over short distances. What are the theoretical ...
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### Standing sound wave tube

If there was a standing sound wave tube and a flammable gas was introduced then ignited, would the combustion be more forceful and more efficient since its following a standing wave, than just a gas ...
112 views

### Why is sound intensity proportional to the square of sound pressure not to sound pressure alone?

I am trying to understand the physical principles behind the sound intensity and sound pressure. As far as i know, sound intensity is proportionate to the squared sound pressure. Can someone explain ...
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### Math formula for crystal glass resonance [duplicate]

For a music therapy experiment, I have to use several crystal glasses with water and different cylindrical shapes, and make them vibrate and produce different sounds. Is there a math formula that ...
324 views

### The shape of speaker cones

This is related to another question I just asked, but they are different enough I thought it deserved its own spot. Speaker elements seem to always be shaped like a cone with a portion of a sphere at ...
115 views

### The physics of sound boards

As a kid I was bemused at why soundboards worked. A small sound could be demonstrably amplified simply by attaching the source to a surface that is rigid and not too thick. How could the volume ...
3k views

### Speed of sound at temperatures below 0 °C

How can the speed of sound be calculated for temperatures below 0 Â°C (down to -40 Â°C)? Does the calculation $v=331\ \frac{m}{s} + 0.6 \frac{m}{sÂ°C} \times T$ still hold (where T's unit is ...
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### How can one calculate the distance a particular sound will travel?

What do you need and how to calculate a distance traveled by sound? For example if you hit a bell with a specific amount of power how far will it travel?
229 views

### How far do air particles move when a sound wave passes through them?

How far do air particles move when a sound wave passes through them? I know that they don't actually travel, the question is how far do they oscillate or what is the physical amplitude of the ...
196 views

### Could submarine SONAR kill a diver?

Could a diver swimming next to a submarine be killed or seriously injured by its SONAR? What physical aspect of SONAR affects the human body in a potential harmful way?
158 views

### Is it possible to estimate the speed of wind by the sound emitted by a cable of an overhead power line?

I was near ($\approx40m$) an overhead power line and I heard a sound coming from the cables of the power line; I think the sound was made by the vibrations of the power cables due to the wind but I am ...
89 views

### Diffraction of sound

The sound waves, by the virtue of it being a wave, shows diffraction and interference. But in diffraction, I learnt that if the wave is allowed to enter through a small aperture, there is a central ...
55 views

### Rijke tube: Why Sound is maximum when heated 1/4th length from bottom of tube

Why is it that the maximum sound coming from a Rijke tube happens only when heated wire gauze is placed at 1/4th the length of the tube from the bottom. According to Rayleigh: If heat be ...
104 views

### Frequency shift without affecting signal length

Non-physicist here. From what I've learned in university and what common sense says, a shift in frequency of a signal results in a change in its length in time. For example, if a sinusoid signal of ...
296 views

### Are pure mechanical evanescent waves possible?

Consider a lattice of massive points connected by harmonic springs, with zero or periodic boundary conditions. If we make a repeating pattern of $N$ varying masses, the system will have $N$ bands of ...
532 views

### Theory behind patterns formed on Chladni plates?

In this video of vibrating Chladni plates we can see small sand particles align themselves into different interesting patterns (also shown in the image below) which correspond to some particular ...
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### Differences of waves in water and air

When one drops a pebble in a body of water, one can observe multiple waves emanating from the point the pebble came in contact with water. Be it because the water "jumps" up and comes back down, ...
104 views

### Modeling sound resonance in an arbitrary cavity

I am trying to solve a challenging problem, and I'm hoping for some advice on how to proceed. I want to model sound waves in a cavity for the purpose of determining resonance. The plan is to answer ...
153 views

### Numerical simulation of sound propagation in air

How does one go about accurately modeling sound propagation in a room (with reflections, absorption, and diffusion characteristics) from the motion of a loud speaker? More specifically what are the ...
113 views

### Can sound be propagated without initial mechanical interference?

I have researched up a little on sound, and it seems that sound is a mechanical wave that propagates through the air as energy, and that is how we hear it through our ears. Depending on the medium's ...
507 views

### Is it possible for a sound to be louder as you move away from it?

I was asked a puzzling question/thought experiment: Given the source of a sound in a wide open field so acoustics do not play a role, is it possible for a sound to be louder as you move away from it. ...