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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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How is sound affected by gravity?

How would sound be different on a planet with a stronger gravitational field? My reasoning leads to sounds of the same wavelength having higher frequencies - is this correct?
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28 views

Power and intensity of a sound wave

So in the case of a point source of a sound wave in a sphere, I'm wondering why the Intensity decreases with $r^2$ because if i setup the formula the Power always increases with $r^2$. So these two ...
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How does speaker in “ROBOCOPP B A S U Ealarm SOS Personal Alarm” works? [on hold]

I was working on a project which required producing a sound with more than 125 DBs...then I found this device I market which claims of producing 130DBs although to my knowledge it produces around ...
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1answer
55 views

Difference in Sound and Heat

What makes sound and heat distinct ? The answer is said to lie in the fact that the former consists of vibration in an ordered fashion while the latter is not. But why would ordered vibration not be ...
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Sound of water filling up a bottle

So there are many questions addressing but I am yet to find a correct response. Most answers indicate that the bottle should be modeled as a Helmholtz resonator or as a closed organ pipe with ...
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0answers
40 views

What does a negative end correction mean?

I was asked this question in one of my tests: "In an experiment to measure speed of sound by a resonating column a tuning fork of frequency 500 Hz is used. The length of air in the column is varied ...
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1answer
34 views

Acoustic permeability of polypropylene

I've searched the web for the coefficient of acoustic permeability of polypropylene but couldn't find any. I have a situation where there's a $3.3(mm)$ thick polypropylene layer over my target, and I'...
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30 views

How low frequency sounds transmitted through wall?

I know in theory that it's wavelength is large enough compare to barrier width. But unable to understand through visualization how low frequency waves passes through it. Why only low frequency wave ...
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1answer
24 views

Amount of pressure embodied by a pressure wave (sound)?

I'm looking into a way to calculate the pressure by which a sound wave at close proximity to the target object impacts. My research led me to this physics site (http://hyperphysics.phy-astr.gsu.edu/...
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2answers
26 views

Why is the speed of sound in air constant (relative to temperature) when the wave speed formula is Vwave = fλ? [duplicate]

By the logic of the wave speed equation, shouldn't a 1000 Hz sound travel twice as fast as a 500 Hz sound? I know it doesn't, but why not?
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2answers
101 views

Do planes have to be noisy?

I tend to think of noise as an undesirable waste of energy because the generator was not designed for that purpose. But that doesnt mean this waste can be avoided. So I wonder how much of this noise ...
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2answers
25 views

Does a dynamic microphone produce a derivative of the input sound waveform?

Consider a common dynamic microphone, where the membrane moves an attached coil in the field of a permanent magnet. I believe that the voltage produced by the coil as the membrane is moving is ...
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2answers
42 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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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
34 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
30 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
65 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
293 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
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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
591 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
51 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
34 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
124 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
22 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
33 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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0answers
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
39 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
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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
23 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
17 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
62 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
602 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
28 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
18 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
26 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
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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
38 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
39 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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38 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
65 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
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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
80 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
82 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
58 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
28 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
587 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
50 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 ...