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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Visualise the sound intensity
I'm studying Biophysics and my current subject is sound. One of the properties of sound is intensity. From my notes I can see the following definition:
Intensity Formula is: $(I = w*m^{-2})$ or $(I = ...
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151 views
What does it mean to increase volume by X decibels?
I am trying to decipher what decibels are:
http://en.wikipedia.org/wiki/Decibel
It seems to be a log ratio of audio amplitude multiplied by a constant. I am confused by what this means though.
If ...
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132 views
Sound waves. Relating the displacement to the pressure function
I am trying to understand some notes my professor has typed up. He writes that we can write a sound wave in terms of the variation of pressure in a medium over time using the function
$$ p(x, t) = P_0 ...
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347 views
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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2answers
757 views
can sound travel is space?
Everybody knows that sound cant travel through space, but is really valid? Here is my scenerio:
Given the size of a football field's length cubed, there are two objects at two opposing sides. the ...
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314 views
Why doesn't sound travel through walls?
If sound travels better through denser material, why does the sound travel better without a dense wall?
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634 views
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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505 views
Why and how is sound produced when two objects hit each other?
When two objects collide and undergo a partially inelastic collision (so every one we experience in every-day life), they rebound to a certain degree, but kinetic energy is not conserved. Thus, the ...
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404 views
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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5answers
506 views
Sound frequency of dropping bomb
Everyone has seen cartoons of bombs being dropped, accompanied by a whistling sound as they drop. This sound gets lower in frequency as the bomb nears the ground.
I've been lucky enough to not be ...
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2answers
644 views
How can sound waves propagate through air?
We know that the sound waves propagate through air, and it can't travel through vacuum. so the thing that help it doing that is the air's molecules pressure. So my question how can that happens? I ...
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127 views
Speaker cabinet to improve sound of mobile phone loudspeaker (music) [closed]
I want to experiment with an enclosure for my phone so the frequency response has a little more punch at the bottom end. I understand that something can't be created from nothing, but enclosures work ...
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2answers
96 views
Sound “exploding” in car's window at certain speed [duplicate]
Possible Duplicate:
Why, when one opens 1 car window, does that noise occur?
My knowledge in this area is really out-of-dated and stopped somewhere like ten years ago. So I would like to ...
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3answers
348 views
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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2answers
284 views
Frequency Specific Sound Reduction And dB Levels?
I started with a DIY construction project pertaining to sound-proofing; but now I'm feeling overwhelmed by a lack of knowledge on the physics of sound.
I've learned that sound reduction techniques ...
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92 views
Sound Produced due to motion of air inside a tube
I'm trying to understand the sound produced by Air motion inside the respiratory system.
If you have a long tube with a suction apparatus at one end , You turn on the apparatus and the air is sucked ...
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114 views
Ultrasonic Nonlinear Acoustics
I stumbled upon the the wikipedia entry on Sound from ultrasound which I found interesting. There is already another question here that referenced this topic.
This got me wondering. Is it possible to ...
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64 views
The sound of coffee [duplicate]
Possible Duplicate:
Why does the sound pitch increase on every consecutive tick at the bottom of a filled cup of coffee?
A colleague suggested this experiment this morning :
Get a cup of ...
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217 views
Open Ended/ Close Ended instruments?
Close ended instruments have twice the wavelength, because the wave must travel twice the distance to repeat itself.
Why must a wave reach a lower density medium (air in this case) to repeat? When ...
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1answer
119 views
Loudspeaker frequency response dip
I'm trying to determine the reason for a dip in the frequency response curve of my loudspeaker. I have a loudspeaker mounted on the inside of an enclosure, and a 100mm ID tube mounted in-front of the ...
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1answer
274 views
Resonance and Natural Vibrations in Vacuum
In my Physics textbook, it says that if two pendulums of the same natural frequency are placed next to each other and if one is set into vibration, the other starts resonating and when the first one ...
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1answer
184 views
What is the roaring in a roaring fire?
I was just starting a barbecue fire by blowing on the smouldering coals when I realised I had no idea what the sound was actually caused by. I can make the sound by blowing at almost any flame I can ...
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2answers
142 views
Can sound be separated from air?
I would like to open up a window in my house, let the air in, but keep the sound out. Could a device be designed to put up on the window, like a screen, and accomplish this?
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493 views
The speed of sound is proportional to the square root of absolute temperature. What happens at extremely high temperatures?
The speed cannot increase unboundedly of course, so what happens?
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249 views
Sound waves through a glass filled with liquid
I was pondering about the following 'experiment', and was curious about the formulae behind it.
Imagine having a glass filled with a liquid. On one side there is a sensitive receiver that records ...
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1answer
306 views
speed of sound relative to density of medium through which sound travels
I know that sound travels faster in water compared to air and say faster in steel than in what're so
What would the density have to be to cause sound to approach the speed of light
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1answer
156 views
Will a black hole increase the speed of sound above the speed of light in this medium
For the sake of this question we are inside the EH and a sound wave enters from our perspective as the sound moves closer to us at the EH would it speed up.
Specifically how would the extreme ...
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2answers
951 views
The energy of an electromagnetic wave
The intensity of an electromagnetic wave is only related to its amplitude $E^2$ and not its frequency. A photon has the same wavelength as the wave that's carrying it, and its energy is $h f$.
So ...
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2answers
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How can I use sound/resonance to clean sewers?
This probably doesn't fit into the realm of regular questions ; it is more of an applied rather than theory/math question ...
Anyway, I'm curious whether a metre diameter speaker fitted over a ...
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1answer
72 views
noise level (units confusion)
i had a question in one of my classes regarding SNR in underwater acoustic channels. There are a couple of terms with the unit dB re uPa. I know it stands for dB ...
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1answer
149 views
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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510 views
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).$$
For sound waves, this ...
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3answers
589 views
Why is there a 90˚ phase angle between particle velocity and sound pressure in spherical waves?
My text says that in a plane sound wave (or in the far field), particle velocity and pressure is in phase. As we move closer to the sound source (to near field and more spherical waves), the phase ...
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2answers
421 views
How does the energy of a sound wave decrease with the distance
More precisely, how small is the potency a listener hears, compared to the potency of the emitter.
I'd like to present a simple and yet reasonable approximation, to a high school audience (I am a ...
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1k views
How does one derive the equation for the speed of sound?
In my acoustics books I see
$$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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Laws of aerodynamics after breaking the sound barrier
my knowledge of physics is not very extensive, so I hope my question isn't too stupid.
I know that when (for instance) a plane breaks trough the sound barrier, the laws of the aerodynamics change.
...
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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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3answers
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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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1answer
173 views
Why does music have a different tonality when heard from earphones a distance away?
Why when I have music on in earphones and I have them resting on a desk, the music sounds different, like in a different tonality/pitch to when I am actually using them?
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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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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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2answers
212 views
How can people do music with Tesla coils?
I saw a lot of videos of Tesla coils doing music on YouTube. And I wonder how can they do that sort of things.
How they can calculate what tone it is going to do? And what are the factors to ...
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1answer
103 views
Will timbre/quality be different if two different people play the same guitar? [closed]
Will timbre/quality be different if two different people play the same guitar? Assume that frequency/pitch and amplitude are same.
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1answer
340 views
How does a speaker produced different sounds?
What I have read is that a speaker produce sound by just moving a coil attached to a cone which moves back and forth. So, If I try to move the coil by hand, would it produce sound? If not why not? or ...
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2answers
180 views
Does EM radiation (any, i.e. RF), or sound, radiate everywhere at once?
I am having trouble understanding electromagnetic radiation (or waves in general, be it EM or sound). If I have a 1 Watt speaker, is it infinitely divided and spread out so that everyone in every ...
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2answers
130 views
Physics of musical theory [closed]
can you recommend some instructive online source where I could find some information about physics of musical theory. It can be either basic or advanced. I'd like to improve my guitar play ...
7
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1answer
259 views
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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3answers
341 views
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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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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766 views
Is it possible to break bulletproof glass with your voice?
In The Adventures of Tintin, an opera singer (the Milanese Nightingale) broke a bulletproof glass case using her voice. Is that scientifically possible?
From the Wikipedia page, a typical bulletproof ...
