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 a black hole produce sound?
I was reading this article from NASA -- it's NASA -- and literally found myself perplexed. The article describes the discovery that black holes emit a "note" that has physical ramifications on the ...
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Why is the bell, well, bell shaped?
What is the significance about the bell shape, when its hit at the rim it rings/produces sound better than other shaped objects? If so could anyone explain a little bit on it.
EDIT: From the ...
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How much information about the scale of a waterfall can be obtained from its sound?
Is it possible to constrain the height, volume flow, or distance of a waterfall from the quantitative analysis of a high-quality recording of its sound?
As an aside, the simulated sounds of fluid ...
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Fourier transformation in nature/natural physics?
I just came from a class on Fourier Transformations as applied to signal processing and sound. It all seems pretty abstract to me, so I was wondering if there were any physical systems that would ...
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Why does the sound pitch increase on every consecutive tick at the bottom of a filled cup of coffee?
Since I don't know the proper physical terms for this, I describe it in everyday English. The following has kept me wondering for quite some time and so far I haven't found a reasonable explanation.
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Why does the fundamental mode of a recorder disappear when you blow harder?
I have a simple recorder, like this:
When I cover all the holes and blow gently, it blows at about 550 Hz, but when I blow more forcefully, it jumps an octave and blows 1100 Hz.
What's the ...
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Why does the note played by a flute not change in this case when the air column is interrupted?
I play the flute as a hobby, and I've noticed that when playing middle D or E flat, one can interrupt the air column by releasing a certain key (which is near the middle of the air column), and yet ...
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What determines the pitch of an explosion?
It's bonfire weekend here in the UK, and everybody is intent on shooting fireworks.
I was wondering, what determines the pitch of the sound produced by an explosion?
The sound has clearly a ...
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Did Felix Baumgartner produce a sonic boom during his jump?
I really got to thinking about this. The speed of sound is measured at 761.2 MPH at sea level. But how does this number change as air density decreases? The lack of air density is what allowed his ...
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Maximum delay for effective active noise cancelling?
Active noise cancelling reduces unwanted sound by sending the inverted phase of the original phase:
(Source: Wikipedia)
Theoretically, this seems logical to me. However, in real life, the ...
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Phonons in non-crystalline media
Do sound waves in a gas consist of phonons?
What about a glass? Or other non-crystalline materials such as quasicrystals?
How does the lack of translational symmetry affect the quantization of the ...
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Why does my natural whistle have a maximum volume
When I whistle, I find that I can vary the volume by pushing more or less air through my mouth at once. However, when I increase volume past a point, I start to hear a blend of rushing air and a ...
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How does paper make sound when it is torn?
We know that from our experience when we tear up a piece of paper, we can hear a characteristic sound. What is the underlying mechanism behind it? What do the dominant frequencies (edit: I don't mean ...
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How can you focus sound?
I saw this TED talk and I am curious as to how the sound is focused on the general level. Can anyone explain this or does anyone have any good articles?
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Octave equivalence: biological or more?
I'm a graduate student in mathematics doing a bit of research in signal processing and Fourier analysis and I've come across a question that could probably be better answered by a physicist:
Is the ...
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How does a steady wind flow generate sound?
When a wind blow through sharp edge, say, edge of a paper, you can see the vibration of the paper and hear the sound.
For this type of oscillation, it should be a damped oscillation with external ...
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Why can I tell a flute from a trumpet?
The usual story I've heard describing the difference between a 440 Hz note played by a flute and a trumpet is that the overtones are different. That is, if you play a note at 440 Hz, there will also ...
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Whistle Physics
I'm looking for a simple explanation of how a whistle operates. I know that forcing air over a sharp lip can set up a wave in a resonating cavity, but how? "Most whistles operate due to a feedback ...
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Does sound propagate further in freezing weather?
A few days ago I went for a walk in the evening. We're having winter with a little snow and freezing temperatures. We're in a quiet, shallow valley with a train station about 1km from us. I heard a ...
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Superposition of electromagnetic waves
The superposition of two waves is given by
$$\sin(\omega_1 t)+\sin(\omega_2 t)=2\cos\left(\frac{\omega_1-\omega_2}{2}t\right)\sin\left(\frac{\omega_1+\omega_2}{2}t\right).$$
For sound waves, this ...
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Is there an upper frequency limit to ultrasound?
Wikipedia has this diagram of the acoustic frequency spectrum:
Is there an upper limit to the frequencies you can transmit through the air? Are they absorbed more and more at higher frequencies, ...
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Hearing a sound backwards because of Doppler effect
Consider a supersonic plane (mach 2) aproaching a stationary sound source (e.g a fog horn on a boat).
If I understand it correctly, the passengers in the plane can hear the sound twice. First at a 3 ...
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Why does thermal resistance go down as temperature goes up?
Here is the thermal resistance data for three speaker coils disengaged from the speaker cone. Any ideas? I would think it would be a horizontal line.
http://en.wikipedia.org/wiki/Thermal_resistance
...
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Difference in timbre between 'quiet' and 'far away'
I'd like to know what are the differences in timbre - or the acoustic properties of a sound - that allow us to differentiate between a sound which is quiet (but close-by) and one which is far away.
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Is it possible to travel at precisely the speed of sound?
I've been talking to a friend, and he said that it's impossible to travel at exactly the same speed as the speed of sound is. He argued that it's only possible to break through the sound barrier using ...
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Can light waves cause beats?
My question is pretty brief. When two sound waves of nearly same frequencies interfere, we get beats.
But, I have not observed something like that happening in the case of light. In fact, most of the ...
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What is sound and how is it produced?
I've been using the term "sound" all my life, but I really have no clue as to what sound exactly is or how it is created. What is sound? How is it produced? Can it be measured?
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2013 Russian meteor event, Sonic Boom or Explosion Boom?
In the lastest meteor event in Russia there was a big BOOM heard long after the meteor had passed. In this youtube video we can see at 4:30 the Meteor passing.. then hearing the BOOM at 7:00 , 150 ...
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Does light have timbre?
Timbre is a property associated with the shape of a sound wave, that is, the coefficients of the discrete Fourier transform of the corresponding signal. This is why a violin and a piano can each play ...
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Riddle about speed
This stems from a riddle I read in a magazine perhaps 20 years ago so I apologise for the imprecise recollection.
A dog that can run infinitely fast is placed on an infinitely large flat surface and ...
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Slinky reverb: the origin of the iconic Star Wars blaster sound
This is a fun problem that I came across recently, which I'm posting here for your delectation. We all love a good slinky: they can be used for all sorts of fun demos in physics. One example is the ...
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Why does water make a sound when it is disturbed?
When I disturb a body of water, what causes the familiar "water moving" sound?
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How does one derive the equation for the speed of sound?
In my acoustics books I see
$$c^2 = \frac{\mathrm{d}P}{\mathrm{d}\rho}$$
where $c$ is the speed of sound, $P$ is the pressure and $\rho$ is the density. Where does this equation come from? In my ...
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How to distinguish female and male voices via Fourier analysis?
What makes one, without looking, be able to identify the gender of the talker as male or female?
I mean if we Fourier analysed the voice of males and females, how the 2 spectrums are different which ...
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What are the limitations of performing music in space?
Canadian astronaut Chris Hadfield's song Space Oddity is making news around the world today. It makes me wonder: What are the limitations of performing music in space? Clearly, there is no point to ...
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_Actually_ hearing the shape of a drum
The problem of hearing the shape of a drum is well known as a mathematical problem.
But what about as a problem of (1) physics and (2) human perception?
Suppose you have the kind of membrane used ...
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Is there a limit to loudness?
Is there any reason to believe that any measure of loudness (e.g. sound pressure) might have an upper boundary, similar to upper limit (c) of the speed of mass?
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There is absolute silence?
Silence is a relative or total lack of sound. But it is possible for real? Is there any way to achieve this?
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If sound wave is going to hit any metals can it make that metal electrons into exited state?
What will happen when sound wave hits the metals with very high frequency can it make the electrons to exited state. If it happens then what will be the state of that metal
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Why does a wobbly metal sheet make the sound of thunder?
In other words, what is the similarity between a lightning bolt and a wobbling sheet that make them sound alike?
It seems to me that the two systems have a much different way of moving the air, and ...
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What is the cause of noise generation at my bike helmet
I am looking for anexplanation of this phenomenon:
I was riding my bike, (not driving it, was sitting on the back seat) with the helmet on. While the glass of the helmet was intact, I could hear ...
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Why is the decibel scale logarithmic?
Could someone explain in simple terms (let's say, limited to a high school calculus vocabulary) why decibels are measured on a logarithmic scale?
(This isn't homework, just good old fashioned ...
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Doppler's effect use
While i was in high-school i learn't the Doppler's Effect which if i remember correctly is:
The Apparent change in the frequency of sound caused due the relative motion between the sound and the ...
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Why does inverting a song has no influence?
I inverted the waveform of a given song and was wondering what will happen.
The result is that it sounds the exact same way as before.
I used Audacity and doublechecked if the wave-form really is ...
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Why echos cannot be heard inside the room?
If I go camping and shout anywhere, in the forest , or on a cliff, I usually hear the echo of my voice.
Why when I shout in my room I do not hear any echos?
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Is it possible to accelerate air to supersonic speeds? What would it look like?
The speed of sound is the rate that disturbances in air propagate through it.
Is it possible to have a wind that itself is moving at supersonic speeds relative to stationary winds around it?
Or ...
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Physics of a guitar
I understand that when you pluck a guitar string, then a bunch of harmonic frequencies are produced rather than just the frequency of the desired note.
If this is true, why does C2 sound so different ...
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Is a soundproofed wall really only as strong as its weakest area?
I've seen a few questions about sound waves and sound travel here on Physics SE, so I'm hoping this question is a good fit for this site.
During my internet research on soundproofing, I've come ...
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How can a Human voice or animal voice have unique frequency
Well this is pretty noobish question and I am not sure how to ask.
When We talk we don't talk in an uniform frequency. Then how can one measure frequency of ones sound/voice ?
I am asking this cause ...
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What happens to sound waves?
I apologize if this is a naive question, but I never really learned about this. I'm curious as to what happens to sound waves after they are "used"? For example, if I say something to you verbally, ...
