👂Sounds that we hear
Every sound you hear is an invisible (for our eyes) vibration that travels through the air, hitting air molecules. This moving vibration is the sound wave.
Sound vibrations create sound waves which move through the air space before reaching our ears.

When the sound wave reaches our ear, it makes our eardrum vibrate, and so we hear the sound produced by the sound wave.
When the sound source is close to us, we hear the sound clearly and loudly. At the same way when the source of the sound (the person talking to us, the TV, the car …) is far away from us – we hear the sound quieter and more indistinct. Why?
Because the sound travel in the form of waves, similar to those generated on the lake surface, when you throw a pebble into the lake.
Why do we hear different sounds, in different tonalities? Why do mom’s and dad’s voices sound different? Because the sounds they generate create different sound waves that make the air molecules move and vibrate in different ways.

🔍 Observation
Get your domino set. Take out the dominoes and arrange them straight one after the other in a row. Make sure the distance between the individual tiles is about the width of the individual domino tile. Now push the first domino tile. What happened?
The falling dominoes created a series of changes, created a chain reaction. When a tile changes its position, it changes the position of the tile after it, and when the second tile changes its position it occur a change of the position of the third tile, and so on.
This is exactly what happens when a sound is generated. It causes air molecules to vibrate and they transfer the vibration to the next neighboring air molecules.