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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Frequency resonance of Bones, and other parts of the human body [duplicate]

Today in class we were learning about states of matter. I found out that in a solid the atoms are vibrating. This caused me to think about how crystal glass will break if an opera singer sings high ...
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Does a sonic pulse in a gas enhance thermal mixing?

I have a sonic pulse consisting of around 10 cycles that is propagated longitudinally through a gas in a tube. If there are thermal differentials in the gas (say between case and central portion of ...
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If I accelerate a mass quickly enough through a short distance (i.e. unit step function), would I create wind, sound, and heat?

As far as I know, the movement of air molecules can result in what we call wind, sound, or heat (and maybe some other things I'm not thinking of), depending on the assumptions about its motion. Wind ...
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Bell in a vacuum, where does the sound energy go?

I'm not educated in physics, but I learned that a bell struck in a small vacuum chamber will not be heard by people around it (in a school science lab). If it had been surrounded by air, there would ...
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113 views

different liquid in a container produce different sound

Does the type of liquid in a container affect the sound it produces? example like milk, water and coffee produce a minute different sound
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Is it realistic for soundwaves under water to “sink” or “float”?

I'm studying soundwaves under water and I had a numerical problem that I was asking about. http://stackoverflow.com/questions/28904017/are-my-matlab-iterations-working Now I wonder if you can tell ...
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39 views

Combining sound absorption coefficients

I am trying to predict the reverberation time in a room with different surfaces and different absorption coefficients (i.e. curtains, wood panels, carpet etc). My question is about how to calculate ...
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72 views

Why does my shirt make a crackling noise when it is static?

I thought that when clothing becomes "static" (used as a colloquial adjective for that state when clothing fresh out of the drier sticks to everything) it's because of a build up of electrons. That's ...
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The Frequency of a Trill

My music teacher recently pointed out to me that, when performing a trill (alternating between two notes very quickly) the finger for the higher note should be placed slightly lower on the string than ...
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22 views

What frequencies will get lost/diminished when you listen to a colloidal speaker without the backside

I was checking the connections of my colloidal speakers, so I had to listen to music without the backside of the speakers. There was clearly a difference in the quality of the music, but I couldn't ...
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What is the exact physics behind sonic levitation

Me and a group of friends decided to choose sonic levitation as our research topic. However, after looking up the theoretical background, we hit a roadblock: (Here is an image of a standing sound ...
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46 views

Can ultrasonic signal be guided through a tube?

I have an industrial application using an ultrasonic sensor to detect whether transparent film is present in a plastic ring. Ring minimum diameter is > 30mm. Sensing distance is 90mm. Sensor ...
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63 views

What's the relationship between sound speed and acoustic phonons?

In the textbook, it says that the slope of the acoustic branch of phonons equals to the sound speed. There are 3 kinds of acoustic phonons including TA and LA phonons. Does it mean that there are also ...
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41 views

A simple question about frequencies, vibrations and engineering

I am a composer that likes science a lot but I am less than amateur at it. I am trying to start understanding how low frequencies (below 100hz let's say) behave. The intent is to find solutions to ...
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75 views

Special Relativity & QuickSilver from X-Men

In the movie X-Men: Days of Future Past, the mutant character Quicksilver possesses the ability to move very fast. A particularly memorable scene in the movie is one where he runs around very quickly ...
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absorption and reflection of sound on molecular level

Can someone explain the reflection and absorption of sound on the molecular level? What really is reflection? Why porous and soft material absorbs sound? What's the definition of soft in terms of ...
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Evolution of normal of material surface moving at a steady velocity

I need some help with the following question: A material surface moves with the fluid with a steady velocity $\mathbf{U_{o}}$. Show that the unit normal $\mathbf{n}$ to the surface evolves according ...
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35 views

Natural frequencies

It's defined as the frequency that an object vibrates at when there is no driving force. What's a driving force? IS the natural frequency the frequency at which the atoms inside vibrate? People ...
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Limits for the linear wave equation

In acoustics and continuum mechanics the following wave equation (for Speed of Sound $c$) for the pressure field $p$ is well-known: $\partial_t \partial_t p = c^2 \Delta p$. This wave equation can be ...
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Sound waves during day and night

A man stands on the ground at a fixed distance from a siren which emits sound of fixed amplitude . The man hears the sound to be louder on a clear day than on a clear night. Why?
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120 views

Why do objects have resonance at natural frequency?

What actually is a natural frequency for an object and what makes it vibrate with increased amplitude when coupled with an external oscillator that matches the natural frequency?
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Acoustics - transition between free field to wave guided propagation of ultrasound

Is there a general formula involving wavelength, transducer diameter and tube diameter that shows where free field propagation transitions to wave guided?
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41 views

Reason behind “marble dropping sound” from concrete

Many people have experienced strange sounds from the ceiling of their home that sounds like marble dropping, often at night when they're trying to sleep. Currently there doesn't seem to have a fixed ...
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Proof of equivalence between soundwaves and phonons in large wavelength limit (Ashcroft-Mermin, ch. 22)

In chapter 22, Ashcrof and Mermin argue that the normal modes of a harmonic crystal are not only formal but precisely equal to the large wavelength limit of acoustic phonons (which sounds, of course, ...
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What sort of waves are produced by tuning forks?is it transverse, longitudinal or both?

We often know tuning forks are used to to produce wave in various experiments that we do in lab. but the matter of concern is what sort of waves are produced by it? is it transverse, longitudinal or ...
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42 views

What does a long strip of explosive sound like when detonated?

By long, I mean something like (say) 2 km of detcord. Or perhaps multiple close spaced charges in a line over that distance, simultaneously detonated. Close up a single piece of explosive produces a ...
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1answer
35 views

Is there a non-relative unit of measurement for the volume of sound?

I understand dB to be the main unit of measurement of the volume of a sound, but (to the best of my limited knowledge), dB only gives a measurement of the volume of a sound relative to the volume of ...
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What is the speed of sound in space?

Given that space is not a perfect vacuum, what is the speed of sound therein? Google was not very helpful in this regard, as the only answer I found was 300 km/s, from Astronomy Cafe, which is not a ...
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Effects of terrain on outdoor sound propagation?

I'm looking for a computationally fast model for capturing the effects of varying terrain topology in far-field outdoor acoustic propagation, and was wondering if anyone had any insight or could point ...
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265 views

Apparent frequency and wavelength in the Doppler effect

For a transverse wave(or for pressure waves required to produce longitudinal waves), the motion perpendicular to the direction of propagation of the wave is governed by an equation like $y = ...
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25 views

Is it possible to realize either the bucket is full or not from sound?

If a bucket is hold under a tap and the tap is open to full the bucket with water, is it possible to understand from the sound of falling water either the bucket is full or not? Are you able to give ...
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300 views

What are the differences between beat and interference?

For two waves, if it can be seen that after an interval of time no sound is heard, which option is liable for this incident? One option is interference of sound, and another is beat. I know that beat ...
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75 views

Does sound have a “louder” direction?

I have a question about the propagation of sound waves. We have two TV's in our house that are almost right on top of each other. One is located on the first floor and the other one is located on ...
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74 views

Can I create a device which will create silence? [duplicate]

Sound waves in opposite phases will cancel each other out. Is it theoretically possible to create a device which will record the sound and output sound in opposite phase which will result in ...
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287 views

How can I hear if something is behind or in front of me?

I wonder how I can hear what direction a sound is coming from. I believe that the brain calculates relative to the volume from each ear, meaning I'm unable to know what direction a sound is coming ...
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59 views

Which modes are excited when a drum is struck?

I've been searching quite extensively for an answer to this question but I cannot find anything definitive. The most I can see is that "one or several" modes become excited, but this is never ...
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Calculating the frequency produced by a rectangular piece of metal

I have a rectangular prism made of steel. Its dimensions are 0.1 cm x 0.2 cm x 12 cm. If I screw one end to a stable object and vibrate the other end. How would I calculate the frequency produced by ...
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What bang / boom sounds do not invoke supersonic propagation?

Explosions, supersonic booms, whiplash sounds are usually supersonic phenomenona. What sort-of common bang / boom sounds are there that do not involve supersonic propagation ? Or is this a "wrong" ...
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34 views

Pressure wave in a cup of tea casued by a bubble burst

Assume there is a cup of tea with bubbles formed on its surface by the inner wall of the cup. If one of the bubbles bursts, it causes a wavefront travelling on the surface of the tea. Is this wave ...
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80 views

Relationship Between Acoustics and Gravity?

I have studied some physics in college, but not enough to know the answer. My motivation: sound (or acoustics in general) does not exist in a vacuum, which means that acoustic waves are only present ...
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1answer
32 views

What does a goniometer (sound) show?

In looking into 2D representations of audio, I came across a tool called a goniometer. I'm aware that a goniometer refers also to a device for measuring angles, but in this context it refers to one ...
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59 views

Transmission of Sound Waves [duplicate]

If a tree falls in a forest and no one is around does it still make a sound ? I know the answer is supposed to be no, because the sound is created when it enters someone's ear. What if I left a tape ...
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245 views

Why do I hear a deep rumble when I cover my ears?

Probably a trivial thing but a simple google search didn't show anything relevant about it. If I cover both of my ears with my hands, I hear a very deep rumble. If I slowly move my hands away the ...
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Why can we produce a sound by blowing across a blade of grass, a paper strip or similar

I just don't know how is the sound produced? Does it come from the vibration of the blade of grass or the air in the up and down?
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3answers
179 views

Resultant frequency if 3 harmonic notes (a chord) is played

If I know the frequency of individual notes being played (let's assume D, F# and A), how do I determine the final frequency if they are played (nearly) simultaneously as a chord. To put the problem ...
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100 views

Why does sound become louder and increase frequency if I give it a narrow path?

If I put my hand over the speaker of my phone like in the picture, I can clearly hear my music amplified, why does this happen? The only cause I can think about is the fact that all the intensity ...
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873 views

How quickly is motion transferred in a solid object?

Just for example: assume an iron bar one foot in length. If you push on one end, the entire bar will move. This seems instantaneous. but actually, from my understanding, the atoms all push against ...
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3answers
102 views

Is it theoretically possible to project sound in a line, like flashlights?

I was wondering if there is a way to project sound waves on a particular point, like a laser? So that you can you can privately send a voice message to a specific person in crowd. The very first idea ...
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55 views

Voices of Animals And Humans

What are the differences between voices of animals and humans? (Not by ear but by a program or similar...frequency, other things) Does each animal in each species have a unique voice? Is there a ...
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105 views

Two superimposed sounds traveling through low- and high-density matter: is separation possible?

Two superimposed sounds (at source: $s(t) = s_1(t) + s_2(t)$; the two sound components overlap completely in time, partially in spectra) travel through low- and high-density matter and are recorded ...