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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How can I calculate wavelength in the following problem? [on hold]

Ultrasonic sound of frequency 100 KHz emitted by a bat is incident on a water surface. What is the wave length of reflected and transmitted sound? (Given that speed of sound in air is 340 m/s and in ...
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1answer
18 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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2answers
37 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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36 views

Space between Gas molecules

We know gas molecules are in random motion. There is obviously space between gas molecules. But I doubt that it is not vacuum,because if it was vacuum then how would the propagation of sound through ...
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20 views

Parabolic Dish / Microphone [closed]

Can anyone help me to understand the characteristics of a Parabolic Dish (Microphone, Audio) and perhaps build a DIY dish?
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16 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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1answer
34 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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10 views

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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14 views

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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21 views

What is the loudest perceived waveform for a given amplitude [closed]

Often missing calls as I don't hear my phone ring, I wish to create a ringtone that sounds as loud as possible. I think it is obvious that amplitude should be as large as possible (with values from ...
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1answer
25 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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1answer
62 views

Russian propeller fluid dynamics [closed]

On a recently launched Russian Diesel-Electric Submarine, the rear Prop has two distinct features. You can see spheres at base of every propellor blade. Also, the trailing edge of the shaft has four ...
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19 views

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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3answers
42 views

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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68 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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0answers
14 views

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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28 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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34 views

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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1answer
54 views

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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39 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
27 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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1answer
18 views

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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1answer
48 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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24 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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2answers
52 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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2answers
70 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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1answer
57 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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1answer
232 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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2answers
53 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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0answers
27 views

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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12 views

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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1answer
28 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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1answer
48 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
28 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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40 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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1answer
146 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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2answers
109 views

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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2answers
79 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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1answer
57 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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2answers
819 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
88 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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3answers
53 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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1answer
99 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 ...
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3answers
55 views

Frequency of Sound Waves

Is the frequency of the echo (resulted from the reflected sound wave) equal to the frequency of the original sound wave?
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39 views

The amplitude of oscillations in sound waves

How can the amplitude of molecules displacement be measured in a sound wave? How can the amplitude of the pressure fluctuation be measured in a sound wave? What are the difference between these two ...
2
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1answer
137 views

Is the change in cochlear potentials dependent on perilymph velocity? [closed]

context: This question may appear to be off topic because it is about the biological particulars of the human ear. Physics can solve abstract models inspired by living organisms, but it is biology ...
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56 views

How does a sonic black hole (or dumb hole) work?

I came across this term and I heard they used sonic black holes to detect something analogous to hawking radiation, but I have failed to find sources which explain how exactly they work and how they ...
3
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2answers
75 views

How would a sound mirror work?

Context: We all know that by galvanizing a plate with a silver coating, this plate will have a very high reflection coefficient and act as a mirror for EM radiation (not for all $\lambda$ ranges of ...
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1answer
42 views

Is the speed of sound related to the speed of impact?

What will be the end result of the following experiment: I take two "identical" buckets of water and a hammer. I strike the surface of the first bucket with a low speed and measure the speed of the ...