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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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2answers
49 views

Electromagnet produces sound from hollow pipe

I have wrapped around a 80cm metal pipe some copper wire and attempted to produce an electromagnet. The electromagnet works nonetheless from the extremities of the metal pipe a sound is being produced ...
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30 views

Is it possible to calculate a flight path of a plane using dB and duration it was heard?

Is it possible to calculate the flight path past a boat of an aeroplane based on the following information? The plane was a prop plane which can be heard at 88 dB at 1000 ft. The plane was cruising ...
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1answer
43 views

What does it mean to hear the gravitational waves?

In last few years, I watched a lot of YouTube videos claiming that gravitational waves can be and has been heard. They also play a short audio signal. How do experiments such as LIGO replicate the ...
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1answer
35 views

Determining the Frequency of a Gong [closed]

I want to build a circular Gong for Sound Healing and I want a specific frequency but I don't know how to calculate it. Does someone can help me?
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1answer
73 views

How does foam “absorb” sound?

I have been reading a bit about sound absorption and reduction. I read that sound can be "reduced" by friction, that's fx. the reason why lightning sound "sharp" the closer you get to it. My question ...
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2answers
659 views

What does warming up a gong do?

This is almost something I'd cross post with the Music SE, but I specifically am looking for physics answers not music answers. When playing a gong, one is often told to "warm up" the gong. This ...
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3answers
6k views

Why does sound not move through a wall? [duplicate]

I'm learning a bit about sound and was wondering: If the speed of sound is determined by the amount of matter the source is surrounded with, why doesn't it go through a wall? Example: Speed of ...
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2answers
612 views

Longest ringing/resonating object [closed]

I am interested in objects which resonate or ring for as long as possible. In particular, I am interested in Crotales (https://en.wikipedia.org/wiki/Crotales), and if it is possible to make a longer ...
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2answers
118 views

Which waves are produced during tuning fork vibration? [duplicate]

In my book, it is written that transverse waves are produced during physical motion of tuning fork. But vibration of tuning fork produces sound which are compressional in nature . Please tell me ...
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1answer
25 views

Will sound be generated by the capture of air from a vacume?

I have a thought experiment. If I had a box sized vacuum sitting on the floor in front of me and I were to instantaneously remove all the walls of my box. Would the capturing of air from that vacuum ...
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0answers
46 views

Chladni Plate subjected to different waves

A Chladni plate consists of a flat sheet of metal, usually circular or square, mounted on a central stalk to a sturdy base. When the plate is oscillating in a particular mode of vibration, the nodes ...
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3answers
200 views

Why is sound “loudness” measured in $dB$ instead of $[P]$?

From acoustics we know that sound is an elastic pressure wave. What our human senses perceive are "loudness" and "pitch" which are related to the amplitude and the frequency. While pitch can easily be ...
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1answer
23 views

Can a pressure wave induce pressure in a liquid it's propagating through?

I have a piece of cylindrical plastic container containing a liquid and sealed at all ends. The bottom seal is a flexible material that can be broken with enough force. The question is then is: can I ...
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2answers
37 views

Speed of a video and Doppler effect

While watching videos at 1.5x or 2x the original speed I often notice a change in the speaker's voice. I am not sure if that is a change in pitch or something else, and was thinking how it could ...
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35 views

Why a musical instrument's string oscillates with many frequencies? [duplicate]

I am trying to understand why when we play a note on a stringed instrument, not only it oscillates with it's fundamental frequency but also the multiples of that. For instance if you play a D on the ...
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1answer
40 views

Why do pipe organ tubes need to have different thicknesses?

In a pipe organ, there are many tubes—long and short, thick and narrow. Each tube presumably resonates at a specific frequency based on its length and produces a distinct note. Why do they have to be ...
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2answers
30 views

Defining an “envelope contour” without specifying a time window (zoom level)

One of the most fundamental terms one hears in the field of acoustics is that of the amplitude envelope, aka the contour, aka the envelope contour. Intuitively this is easy to grasp as the area formed ...
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1answer
25 views

How can I quantitatively compare the average sound intensity of two different audio clips? [closed]

Let's say I have two different sound clips of two different people snoring. The intensity of the audio in both clips will be fluctuating throughout and peak when the person is inhaling. Is there an ...
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0answers
18 views

Sound wave specifics

Why is it that when standing at the foot of a 30 foot high stockpile of rock (covering at least 5 acres) I can't hear a rock crusher as much as I can 20 yards away from the stockpile of rock?
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1answer
69 views

Why are higher frequencies amplified less by filling a bottle with warmer water instead of colder water?

Out of curiosity I was trying to figure out what makes the sound of hot water versus cold water filling a bottle different, but I'm unable to find any explanation as to why such differences occur. ...
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3answers
625 views

Why use ultrasound for medical imaging? [closed]

What advantage does ultrasound have over sound between 20-20000Hz that it is used in medical imaging over sound in that frequency range?
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2answers
25 views

Sound boom the other way around?

We know the sound boom - but is there any effect if a body decreases the speed underneath the sound barrier?
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1answer
57 views

Can we replicate the sound of thunder with just the lightning?

Scientists are able to extract sound of a two black holes merging from the data they collected without actually hearing it, but we don't know how it actually sounds, that's just a representation of ...
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1answer
24 views

Acoustics transmission through speaker grills

I am measuring the frequency response(5KHz - 20KHz) of a small dynamic speaker driver with the stainless steel grill and without the grill. Without the grill the response is what I would expect. ...
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0answers
34 views

Acoustics - Why does flexible plastic make a noise when flexed?

I have recently been a able to acquire the diffusion layer of a broken TV (the sheet of plastic is about a few millimetres in thickness) and have noticed when flexing it, it makes an unusual, hard to ...
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1answer
57 views

Question regarding sound waves [closed]

An airplane is flying overhead at $150 \; \mathrm{m\,s^{-1}}$ whilst emitting an engine noise with frequency of 1 kHz. What frequency sound wave would a stationary observe hear once the airplane has ...
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0answers
58 views

Harmonics in a tube closed at one end

I have been learning about sound and how a tube closed at one end only seems to have odd harmonics. However, I have found that although clarinet follows this and plays only odd harmonics, saxophone ...
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1answer
43 views

Heat capacity due to Phonon Vibrations

Why does the speed of sound come, in the expression of Heat capacity, from phonon vibrations?
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0answers
60 views

Faraday waves and Chladni plates

I am a High school student who's writing a research paper about Faraday waves and Chladni plates. I've been doing a lot of research on Faraday waves specifically, as there aren't many sources that can ...
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2answers
86 views

Why the faster you spin the highest the pitch get in a whirly tube? [duplicate]

I would like to understand why the faster you spin, higher normal modes are excited This is the tube i'm talking about, i think it's used as a kid's toy: https://www.youtube.com/watch?v=eCOZxzO3FvE ...
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0answers
71 views

sounds of polygonal ring chimes of metal

Suppose we have a number of rings, each of them is constructed from some mass of wrought iron or steel: each ring is a polygon, which I would like to suppose is constructed without welding (so they ...
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1answer
124 views

How are sound waves produced?

I have been utterly confused as to what exactly happens in a sound wave and how it is produced.I understand the mathematical description of it quite well, what I don't get is its qualitative ...
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1answer
90 views

Is the first harmonic the prevalent frequency? [closed]

Why, when we play a string, almost all of the energy we give them is ''used'' in the first harmonic (the fundamental frequency) rather than be distributed between all of them?
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1answer
72 views

Resonant frequencies in air filled closed cylinder

I want to calculate the resonant frequencies of a closed cylinder covered with rigid walls. The cylinder is of dimensions: diameter = $1m$, length = $1m$. Would this fundamental mode formula be ...
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0answers
56 views

Change in pitch on a flute due to blowing at a different angle

Why is it that the location of where the air hits the inside of a tube, the pitch is affected? When playing the flute, directing the air downwards lowers the pitch. Another student suggested that this ...
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4answers
631 views

Sound waves in different octaves

How do the sound waves compare between different octaves? Why is it that you can play a low c and a c, and they are at different frequencies, but the same tone? An octave above a note is the fourth ...
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2answers
71 views

How does the green function for the wave equation in three dimensions preserve the ordering of noises between a speaker and a listener

I was provided with the following equation in class for the Green's function of a three dimensional wave equation: However, I am confused as to how this form of the Greens function preserves the ...
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4answers
2k views

Light propagating through a sound wave

We know that the speed of light depends on the density of the medium it is travelling through. It travels faster through less dense media and slower through more dense media. When we produce sound, a ...
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2answers
76 views

Is it true that we can speak, sing, and play wind instruments due to the Bernoulli effect? [closed]

Is it true that we can speak, sing and play wind (brass) musical instruments due to the existence of the Bernoulli's Principle ?
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50 views

Why does Stirred (rotating) coffee alters cup’s resonance frequency? [duplicate]

I place a spoon in my cup of (dolce gusto lungo) coffee and tap the bottom of the cup with my spoon. It emits a certain (fixed) frequency. However, if I stir the coffee (but not so fast that the ...
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1answer
87 views

How does acoustic impedance change with frequency of the wave and thickness of the medium?

I read in many posts that the acoustic impedance of a material is usually defined as $Z = pc$, where $p$ is the density of the material under consideration and $c$ is the speed of sound in that ...
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1answer
26 views

Is there a way to calculate the $Q$-factor?

I’d like to calculate the $Q$-factor for an acoustically resonating object. I’d like to keep the tests to a minimal, none if possible. Is there any way to do this?
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1answer
78 views

How to calculate the amplitude increase by resonance?

If you know the natural frequency of an object, how would one calculate how much the amplitude increases because of resonance? I would imagine it would depend on the material?
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1answer
82 views

Does the supersonic aircraft feels less air resistance than when it flies with velocity less than sound

When ever I see pictures like this of some object flying at speed greater than sound , I see triangular waves . So I got question in my mind that Do supersonic objects weather its bullet or aircraft ...
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1answer
40 views

How to find acoustical output of a horn?

If I had a horn or cone that could be written as a function $f(x)$ rotated around the x-axis, how would I calculate the output, knowing the input (intensity, frequency, everything)? I want a way to ...
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2answers
97 views

Why do popcorns sizzle after popping?

Why do popcorns make a sizzling sound after popping? At first I thought it might be due to moisture, but according to this, that is not the case, as the water present in the corn has already ...
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0answers
74 views

What does Webster's Horn Equation give?

When you solve the Webster Horn Equation, I've seen in papers that you often get a term $\phi$ which is supposed to represent velocity potential, but I've also seen $P(x)$ which is supposed to be ...
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1answer
56 views

Why normal component of particle velocity must be continuous at boundary?

I have problems for understanding the following: Source: https://mycourses.aalto.fi/pluginfile.php/393850/mod_resource/content/1/Lecture7.pdf Why there would be a vacuum at the boundary? I dont see ...
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0answers
18 views

Is it possible to find acoustic amplitude at a certain frequency if you are given dBA?

I was wondering how one would find the acoustic amplitude of a sound wave if you knew the dBA value of that sound wave?
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9answers
3k views

If sound is a longitudinal wave, why can we hear it if our ears aren't aligned with the propagation direction?

If a sound wave travels to the right, then the air molecules inside only vibrate left and right, because sound is a longitudinal wave. This is only a one-dimensional motion. If our ears are oriented ...