Question

SOUND. What is it. High and low tones. How do we hear? How to save sound historically?

Answer 1

Sound is a longitudinal mechanical wave. Mechanical wave means it needs physical medium to travel (air, water, some particles of matter), longitudinal means that unlike water waves the oscilations move in the direction of the wave, whilst with water as mentioned the water surfaces oscilates up and down thus perpendiclar to the direction of the wave.
A slinky can demostrate this rather well.

Image taken from: https://www.researchgate.net/figure/Illustration-of-a-transverse-wave-and-a-longitudinal-wave_fig6_327447483

Check out the video for demonstration

The frequency of oscilations determines the high or low pitch of the tone. The sound thus travels through air all the way into our ears where it transfers the oscilations onto our eardrums that then oscilate back and forth just like the bass speakers oscilate back and forth when they produce sound. The sound is than transfered through our hearing bones to the cochlea, a snail like organ in field with fluid in which we have stereocilia, hearing hairs that swing in the rythm of vibration of sound. Different stereocilia pick of different frequencies and transfer them into the hearing part of the brain.

Check out the video for more interesting information:

Sound can be recorded mechanicaly (cylinders, vinly records, cd-s), or magnetically (8-tracks, cassets, tapes, hard disks etc.)