# 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?

• This is very vague/general, but a fair question still, so I think it should stay open. Commented Nov 2, 2010 at 19:56
• I find this too wikipedia like question. en.wikipedia.org/wiki/Sound can you be a little more specific. Commented Nov 2, 2010 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.

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 MikeJarman's visualization on YouTube: How Air Molecules work.

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.

• 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. Commented Nov 2, 2010 at 21:58

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 strumming 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 larynx and makes it vibrate. Try this by talking and putting your hand on your larynx, and you can feel that it vibrate.

Sound is a form of energy. And what does sound do? It provides the sensation of hearing. But that's just what the definition tells us. Sound is a mechanical wave. Now just by seeing that you must realise it needs a medium to propagate and must also ask yourself how does a wave propagate in a medium. Well; whenever there's a disturbance in a medium, a wave is produced. Therefore when we apply energy to anything, it disturbs the medium which in turn disturbs the air which helps sound to travel. And i do now undundrstan what you mean by measuring sound, we can measure characteristics of it but do specify what do you mean by 'measuring sound'

• This does not seem to fully answer the question Commented Jan 29, 2018 at 10:06