What I learnt at my job

A sound is comprised of a mixture of a lot of sound waves in different frequencies. Those we could hear are from 20 Hz to 20 kHz. So there are quite a number of frequencies in the audible range. All these frequencies are a single oscillation pattern of the particles, so each frequency is like a singularity.

Let's put it this way. Mr. 440 Hz is a hardworking man. He works everyday, never misses a single day, he regularly takes a vacation on 7th July till 10th July to Mallorca, He has a konstant pattern of life, and he's in the middle class of his society. He doesn't hurts, but it's really monotonous. A single frequency sound is what we call monotone. Have you heard a 440 Hz sinus sound wave? It's that sound that comes out at the 90s, when you switched on the TV's at the 90s, and the broadcaster has nothing to display anymore except this:

That's monotone. 

Now if Mr. 440 Hz meets Mr. 450 Hz, Miss 1000 Hz or many many other frequency, they started to form a mixture of tons. That's what we call sound. But if they all are just busy with themselves and doing stuffs their own in different phases and time interval, you have what we call noise. Cuz a noise comprised of tons in different phases moving in a random pattern. 

Now if they start moving together with each other in an orderly manner and in phase, each with their own role in each given time interval, that's when we have a harmonic sound. 

It's quite astonishing though in some sense because that's just how the nature and a society work. Everyone just taking care of themselves and we have chaos. Everyone helping each other and we start having a functioning society.

That's what I learnt at the acoustic lab.