What is sound? Sound is a form of energy made by vibrations. When an object vibrates, it causes movement in the air particles. These particles bump into the particles close to them, which makes them vibrate too causing them to bump into more air particles. This movement is called sound waves.
We have learnt that sound is produced by vibration of matter. Sound waves reach our ears by travelling through the air. In dry air at 20 °C (68 °F), at sea level, the speed of sound is 343 metres per second (1,125 ft/s). This is 1,234 kilometres per hour (767 mph), or about a kilometre in three seconds or a mile in five seconds.
Although we can hear sound waves we cannot see them with the naked human eye. We perceive sound when vibrations are registered in the brain. When the vibrations are fast n you hear a high note. When the vibrations are slow, it creates a low pitch The sound waves in the diagram show the different frequencies for high and low notes.
Picture a stone thrown into a still body of water. The rings of waves expand continuously. The same is true with sound. Irregular repeating sound waves create noise, while regular repeating waves produce musical notes.
Think about this for a little while. What if the world was completely silent. No sound at all. We couldn’t hear a single thing. We wouldn’t know when an ambulance is coming. We couldn’t hear a train that is coming. It would be dangerous to even go outside.