# 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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This is very vague/general, but a fair question still, so I think it should stay open. – Noldorin Nov 2 '10 at 19:56
I find this too wikipedia like question. en.wikipedia.org/wiki/Sound can you be a little more specific. – Bernardo Kyotoku Nov 2 '10 at 20:05

In general usage, "sound" refers to our perception of the vibrations of particles (atoms, molecules) in some medium, typically air or water, though sound waves can travel through any medium.

Vibrations are produced whenever objects cause the particles in the medium to oscillate, e.g. clapping your hands together, beating a drum, or yelling.

Sound can be measured the way it is heard - just as air molecules begin to vibrate in the presence of a vibrating object - the air molecules can cause other things to vibrate (such as our eardrums, or a part of a microphone) and we can quantify the level of sound by measuring the motion of the detector in any number of ways.

At a deeper level, sound waves are the "Goldstone modes" corresponding to broken translational symmetry of the surrounding medium.

Let me try to bring this a little more down to earth. Think about a parcel of air, large enough to contain a lot of air molecules, but not so large that there are sizable air currents swirling within. We can think of this in an ideal situation as being a fluid of uniform density. This fluid has translational symmetry - if I translate it a little in any direction, it looks more or less the same "in the bulk". Translational symmetry is a continuous symmetry, so I can squeeze the air in a spatially-varying way. It turns out that if I do this in a wavelike pattern with a long wavelength, this is an excitation that costs very little energy, and hence will be important to the physics. These waves are precisely sound waves. This probably doesn't make much sense as I've written it, so I may try to edit this a bit later on if anyone is actually interested in this point of view.

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Sound is air molecules hitting each other, bouncing back, then again hitting each other, and so on. This back-and-forth movement is called vibration. Sound is produced when something like a drum vibrates, and starts the aforementioned bouncing of air molecules. Sound is picked up inside your ears by eardrums, which are like reverse-drums, in that they vibrate with the air molecules. This vibration is then converted to biochemical signals which travel to your brain.

There is a Mickey Mouse visualization here on Youtube:

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What it sound?

Sound is nothing but a mechanical wave. The human ear can detect mechanical waves from 20 Hz to 20,000 Hz.

How is it produced?

It is produced when energy transformation occurs. For eg. beating a drum - mechanical energy.

Can it be measured?

Yes, it can be measured by the frequency of the wave.

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The unit of "sound" is not "hertz" ... A sound wave is characterized by its frequency in Hz, OK but this wave has other characteristics also. – Cedric H. Nov 2 '10 at 21:58
Edited, thanks. – tsudot Nov 2 '10 at 22:02

sound is basically produced by vibrating by either blowing through something like a flute or a recorder, hitting something like a drum, shaking something like maracas, or struming something like a guitar when you do all sorts of these things the air goes through the instrument and hits each side of it to make it vibrate for example when you talk the oxygen goes through your larings and makes it vibrate try this by talking and putting your hand on your larings and you can feel it vibrate.

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Hi cleo. Welcome to Physics.SE. Please don't add your personal info in your posts (more generally questions). You could add them in the about me section of your profile. So, I've revised it :-) – Waffle's Crazy Peanut Feb 2 '13 at 12:46

## protected by Qmechanic♦Feb 2 '13 at 12:23

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