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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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 ...
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1answer
378 views

Why are there usually grids in front of sound speakers?

Usually, the sound speakers have this metal grid. However, not all of them have this. Is there any purpose, maybe related to the sound quality, that justifies this? Or is it only for physically ...
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1answer
6k 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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1answer
119 views

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, ...
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1answer
277 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 ...
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2answers
371 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 ...
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1answer
16k views

Outdoor Active Noise Canceling Speaker [closed]

I would like to understand how to create an active noise canceling system to reduce the noise coming from a street road bump. The advantage is that the area the noise is coming from is very small.
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4answers
52k views

Do low frequency sounds really carry longer distances?

It is a common belief that low frequencies travel longer distances. Indeed, the bass is really what you hear when the neighbor plays his HiFi loud (Woom Woom). Try asking people around, a lot of them ...
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2answers
249 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 ...
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7answers
3k 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. ...
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3answers
327 views

Why does the sound of a tuning fork change as we walk away?

This is a question I got for my class. We have the following situation. We take two tuning forks, we hit them, then we take one of the tuning forks and walk away with it. The sound changes as we walk ...
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4answers
637 views

what could generate a high-pitched whine in electronics where the frequency depends on the current?

So I was operating a Laue machine recently which generates x-rays and fires them at a sample, and I noticed that there was a high-pitched whine coming from the instrument (nothing abnormal, just ...
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2answers
445 views

Does sound cancel itself out?

If there are two 10 x 2 x 1 foot rectangles in space and they are lined up so if they hit each other there will be no spots that are not hit in the front of the rectangle. Then they are pushed forward ...
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0answers
91 views

Sound localization using cross-correlation

I am using cross correlation for sound localization. I have a four microphone array (arranged linearly). My problem is, sometimes the time diff found by cross correlation between a given pair of mics ...
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1answer
103 views

Why are waves, the means, of information transfer over long distances, excluding difusion or contact of info stored in matter

Practical long distance communication, which does not rely on the movement of encoded configurations of matter, from source to destination(odor,books,DNA,floppy disk), always involves waves (EM, ...
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2answers
200 views

Why does this cowbell appear to vibrate at the wrong frequencies?

The cowbell in question: http://www.youtube.com/watch?v=OuU0BzXm-qk In most cowbells, the larger the metal dome, the lower the frequency produced. What would cause a phenomenon where the opposite is ...
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1answer
370 views

At what frequency would a quartz crystal shatter?

Would it be possible to emit a sound at such a frequency that a quartz crystal inside of a watch would shatter? (Rendering the watch useless)
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1answer
362 views

The Mysterious Reverb in a Jar of Hair Gel

I have a small jar filled with hair styling gel (or, as it calls itself: Ultra Gel-Wax). The jar is cylindrical(with the height being less than the width), has an unscreweable lid and is made of ...
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1answer
84 views

Algorithm to simulate impulse response of a solid?

There are well-documented methods of calculating the impulse response of a room (ex. image method, ray-tracing method); however, I have not been able to find anything similar for the impulse response ...
5
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1answer
628 views

Speed of sound in non-newtonian fluids

Recently I saw some videos of non-newtonian (shear-thickening) fluids like corn starch mixed with water(sometimes known as oobleck), where the fluid is placed on top of a speaker cone and starts to ...
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1answer
837 views

How to Calculate temperature, given speed of sound and relative humidity?

I know the solution in reverse direction, but I find it very complex to go the other way around and calculate the temperature when given the speed of sound and relative humidity, any ideas?
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0answers
70 views

Sound Intensity Measurements convert to Sound Power

If you need to have Sound Power results and the location that the microphone needs to be to make the measurement(per the standard) is not accessible. There is a machine part in between the ...
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1answer
1k views

How does concave bowl amplifies the sound?

I recently came across an article / answer in Quora see here that mentioned that if we place the iPhone in a bowl and play music, the volume is amplified. What is the physics principle behind this?
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3answers
817 views

Relationship between Stoke's law of sound attenuation and the inverse square law

In attempting to find a reference for explaining sound propagation, I came across this article in Wikipedia: Stokes law(sound attenuation) What I learnt in high school is that sound is propagated by ...
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1answer
786 views

If the source of sound is vibration, why can't we “hear” a object whose molecules are vibrating?

According to our physics textbook, the source of sound is vibration. According to our chemistry textbook, substances in solid state have molecules vibrating in a fixed position. So why can't I hear my ...
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2answers
81 views

Why does the echo of the last chord appear to rise in pitch

I - and others - observe that when a musical performance ends, the echo of the last chord appears to rise in pitch by up to a quarter tone while the echo decays. This effect appears to be independent ...
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1answer
618 views

How to determine the positions of two points in a radial line by an intensity level dB?

The following is the question from my school. A source emits sound uniformly in all directions. A radial line is drawn from this source. On this line, determine the positions of two points, 1.00m ...
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1answer
254 views

Why doesn't sound infinitely loop?

Let say we have a microphone and a speaker. The microphone will receive the surrounding sound, and the speaker will amplify it. Assume we have unlimited power for the microphone and speaker, so they ...
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1answer
2k views

Simple explanation of relation between speed of sound and r.m.s. speed?

In an ideal gas, the speed of sound $v_s$ is related to the r.m.s. molecular speed $v_m$ by $$\frac{v_s}{v_m}=\sqrt{\frac{\gamma}{3}} \qquad ,$$ where $\gamma=C_p/C_v=7/5$ for a diatomic gas. I ...
2
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1answer
277 views

The Doppler effect in a medium like air (sound) versus the electromagnetic Doppler effect

When you have a listener and a source, and when one of the two move relative to the other, the frequency perceived by the listener will be different. Example: If the listener travels toward the ...
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5answers
421 views

What are those characteristics by which every sound can be identified uniquely?

I have very basic question regarding sound I tried to search it over google but couldn’t find the right answer, my question: ...
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0answers
50 views

Is it possible to estimate the number of people in a room from a limited number of simultaneously recorded audio samples?

Note: I struggled to decide the appropriate site for this question, between http://physics.stackexchange.com/, http://avp.stackexchange.com/, http://math.stackexchange.com/, and even ...
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1answer
461 views

Non-linear waves and shock formation

In the cases of non-linear acoustics, why is shock formation unlikely when the dispersion is strong when compared to the non-linearity of the wave?
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14k views

What is the meaning of “frequency of a human voice”?

The term frequency for a periodic wave can be defined as the number of times a repeating pattern occurs in a given time period (eg: no. of crest and trough cycles per second for EM wave). But what ...
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1answer
1k views

Resonance Experiment

Today in high school physics class, we performed an experiment on the resonance of sound, with a set up like this... To put it simply, the sound waves are supposed to rebound with the surface of ...
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2answers
316 views

Can a sound like a sonic boom change a object like a wall? And how the light on the walls will be changed after a sound like this? [closed]

Can a sound like a sonic boom change a object like a wall? And how the light on the walls will be changed after a sound like this? .
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0answers
60 views

Modeling Acoustic Lubrication

I thought about posting this question in the Biology StackExchange site but really it is just the application of my question that applies to biology not the core of the question itself. Can anyone ...
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1answer
55 views

How could you minimize sonic boom at the ground level?

I've heard that one of the reasons that we don't have commercial supersonic flight is because of the sonic boom produced. Is this really a deal-breaker and if not, how do you get around/minimize the ...
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1answer
753 views

Open pipe resonance

I read somewhere, a closed pipe has resonance with a sound of wave length 4 times the length of pipe (from open end to closed end), when putting a source above the open end (since it reinforces the ...
0
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1answer
279 views

'Push' in a rigid rod travel at speed of sound or speed of light [duplicate]

Two person, $A$ and $B$, each holding one end of a long solid rod. Now person $A$ pushes the rod on one end. Question: Is it correct that the information that the rod has been pushed will travel ...
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1answer
1k views

Why do you only hear high frequencies when a microphone is near its speaker?

The phenomenon I'm talking about is positive feedback, as known from control engineering: when the microphone is too close to its speaker, it can "hear itself", so the signal will be infinitely ...
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2answers
2k views

Why does a glass breaks when subject to very sharp sound like in opera?

I have seen in Ripleys believe it or not that an opera singer generates a very high frequency of sound and breaks a glass window.How do they do it?
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1answer
261 views

Why is there a sharp cracking sound when we break a plastic ruler?

Why is there a sharp cracking sound when we break a plastic ruler? The question appears to be simple and common but I need a apropriate answer.
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2answers
634 views

Heating coffee by yelling?

Is it a myth that yelling to a coffee mug will heat it? I have been hearing my friend saying that screaming will heat coffee or water.
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2answers
648 views

Relative velocity of sound

Relative velocity of sound. As I know that speed of sound in medium is property of medium. And independent of source motion but depend on motion of audience or observer and motion of medium. But it ...
5
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2answers
999 views

Do asteroids create sonic boom while entering the atmosphere?

Because of the lack of any materials to propagate sound, it can't spread in space. There's the air in the atmosphere, but its volume mass increases constantly (either linear or exponential, I don't ...
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3answers
866 views

Measuring speed of a vehicle

I'm very primitive with my thought. So please help if you can in layman terms with an answer to this question. Here we go- by using a street power pole as the source responder, is it possible to read ...
13
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2answers
489 views

How small can you be and still hear?

According to my understanding, at the smallest level sound is just a collection of particles colliding on a wave. So, assuming we can arbitrarily reduce the size of any human being, how small can we ...
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2answers
326 views

Steel rod to Mars vs the speed of sound, how is supersonic travel possible?

I remember reading this passage in the "Feynman Lectures", where Dr. Feynman describes an experiment in which a theoretical metal rod of length equal to the distance between Mars and Earth is arranged ...
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2answers
1k views

FFT distortion, harmonics (singing wine glass)

I'm doing a school assignment on Singing Wine glasses (you rub the rim of the wine glass with a wet finger and it produces a pure tone). I have recorded $30\,\text{ms}$ of the "singing" at a sampling ...